A quality improvement evaluation of a standardized intervention for children with medical complexity transitioning to adult care.

Children with medical complexity have medical fragility, chronic disease, technology dependence, and high healthcare use. Their transition to adult health care at age 18 involves medical and social elements and follows no standardized process. Our goal was to improve transition readiness in children with medical complexity using a transition intervention within a Complex Care program. All children with medical complexity aged 14 to 18 were included in this quality improvement (QI) project (n = 54). We conducted a pre- and post-intervention chart review to assess transition outcomes and implemented a transition intervention for 6 months, which included an age-stratified checklist, charting template, and transition rounds. Before the intervention, 72% of 17- to 18-year-old patients had documented transition discussions, which increased to 86%. Patients with a family physician increased as well (61% to 73% for 17- to 18-year-olds). Three transition education rounds were held. The intervention increased transition readiness, provided tools to facilitate transition, and created a forum for conversation.

Caregiver and Care Team Perceptions of Online Collaborative Care Planning for CMC.

BACKGROUND AND OBJECTIVES: Care plans summarize a child with medical complexity's (CMC) medical history and ongoing care needs. Often, the health care team controls the care plan content, limiting caregivers' ability to edit the document in real time and potentially compromising accuracy and utility. With this study, we aimed to provide caregivers of CMC with online access and shared editing control of their child's care plan and to explore the experiences of caregivers and care team members (CTMs) after using an online collaborative care plan (OCCP). METHODS: Caregivers of CMC were recruited from a tertiary complex care program to use an online, patient-facing platform for 6 months, which included the ability to edit and share their child's care plan. Caregivers and CTMs participated in semi-structured interviews to explore their experiences in using the OCCP. Consistent with grounded theory methodology, a constant comparative analysis was used, which allowed for theoretical sampling and theory generation. RESULTS: A total of 15 caregivers and 20 CTMs completed interviews. Interviews revealed 3 major themes and 9 subthemes, including (1) the navigation of uncharted roles (trust, responsibility), (2) the requirements for success (electronic medical record integration, online access, collaborative care plan review), and (3) cohesive care (accessibility and convenience, being on the same page, autonomy). Themes informed the creation of a theoretical model for the implementation and utility of OCCPs. CONCLUSIONS: Online, collaborative care plans, when implemented safely and thoughtfully, promote shared understanding, improve caregiver autonomy, and increase the accessibility of health information. Together, these benefits facilitate cohesive care and authentic partnership between caregivers and CTMs in the care of CMC.

Association of medications for opioid use disorder with reduced risk of repeat opioid overdose in Medicaid: A cohort study.

INTRODUCTION: Following a nonfatal opioid overdose, patients are at high risk for repeat overdose. The objective of this study was to examine the association of MOUD after nonfatal opioid overdose with risk of repeat overdose in the following year. METHODS: This retrospective cohort study analyzed Missouri Medicaid claims from July 2012 to December 2021. The study identified opioid overdoses occurring between 2013 and 2020 using diagnosis codes for opioid poisoning in an inpatient or emergency department setting. The study implemented Cox models with a time-varying covariate for post-overdose receipt of MOUD. RESULTS: During the study period, MOUD receipt after overdose more than tripled, from 4.8 % to 18.9 %. Overall, only 12.1 % of patients received MOUD in the year after index. MOUD during follow-up was associated with significantly lower risk of repeat overdose (HR = 0.34, 95 % CI = 0.14-0.82). Out of 3017 individuals meeting inclusion criteria, 13.6 % had a repeat opioid overdose within 1 year. Repeat overdose risk was higher for those whose index overdose involved heroin or synthetic opioids (HR = 1.71, 95 % CI = 1.35-2.15), but MOUD was associated with significantly reduced risk in this group (HR = 0.34, 95 % CI = 0.13-0.92). CONCLUSIONS: MOUD receipt was associated with reduced risk of repeat overdose. Those whose index overdoses involved heroin or synthetic opioids were at greater risk of repeat overdose, but MOUD was associated with reduced risk in this group.

Caregivers' Experiences With a Web- and Mobile-Based Platform for Children With Medical Complexity and the Role of a Live Platform Coach: Thematic Analysis.

BACKGROUND: Children with medical complexity (CMC) are individuals with complex chronic conditions who have substantial health care needs, functional limitations, and significant use of health care. By nature of their health status, they have many care providers across multiple settings, making information sharing critical to their health and safety. Connecting2gether (C2), a web- and mobile-based patient-facing platform, was codeveloped with families to support and empower parental caregivers, improve information sharing, and facilitate care delivery. C2 also provided a live platform coach to conduct parental feedback and coaching sessions, which included answering questions, providing advice on usage, and addressing technological issues. OBJECTIVE: This study was conducted to understand the experience of parental caregivers using the C2 platform and the role of the live platform coach. This study is a subset of a larger study assessing the feasibility of C2 in the care of CMC. METHODS: Parental caregivers (n=33) participated in biweekly sessions to provide feedback and receive real-time platform use support from a trained research team member acting as a live platform coach. Parental caregivers were asked about the utility and usability of C2's features. Questions, platform issues, and feedback were recorded on a standardized electronic data collection tool. A thematic analysis was performed to analyze parental comments, and codes were categorized into key themes. The number of comments corresponding with each code was quantified. RESULTS: A total of 166 parental feedback and coaching sessions were conducted, with an average of 5 sessions per parental caregiver (range 1-7). There were 33 (85%) parental caregivers that participated in at least one coaching session. Technical issues and difficulties navigating C2 were addressed in real time during the sessions to encourage platform engagement. Four key themes were identified: (1) live platform coach, (2) barriers to platform usage and technical challenges, (3) platform requests and modifications, and (4) parent partnership and empowerment. CONCLUSIONS: Parental caregivers describe C2 as a valuable tool, acting as a facilitator for enhanced care coordination and communication. Parental caregiver feedback showed that the live platform coach was a critical tool in educating on platform use and addressing technological concerns. Further study of the use of the C2 platform and its role in the care of CMC is needed to understand the possible benefits and cost-effectiveness of this technology.

Evaluation of a Secure Messaging System in the Care of Children With Medical Complexity: Mixed Methods Study.

BACKGROUND: The Connecting2gether (C2) platform is a web and mobile-based information-sharing tool that aims to improve care for children with medical complexity and their families. A key feature of C2 is secure messaging, which enables parental caregivers (PCs) to communicate with their child's care team members (CTMs) in a timely manner. OBJECTIVE: The objectives of this study were to (1) evaluate the use of a secure messaging system, (2) examine and compare the content of messages to email and phone calls, and (3) explore PCs' and CTMs' perceptions and experiences using secure messaging as a method of communication. METHODS: This is a substudy of a larger feasibility evaluation of the C2 platform. PCs of children with medical complexity were recruited from a tertiary-level complex care program to use the C2 platform for 6 months. PCs could invite CTMs involved in their child's care to register on the platform. Messages were extracted from C2, and phone and email data were extracted from electronic medical records. Quantitative data from the use of C2 were analyzed using descriptive statistics. Messaging content codes were iteratively developed through a review of the C2 messages and phone and email communication. Semistructured interviews were completed with PCs and CTMs. Communication and interview data were analyzed using thematic analysis. RESULTS: A total of 36 PCs and 66 CTMs registered on the C2 platform. A total of 1861 messages were sent on C2, with PCs and nurse practitioners sending a median of 30 and 74 messages, respectively. Of all the C2 messages, 85.45% (1257/1471) were responded to within 24 hours. Email and phone calls focused primarily on clinical concerns and medications, whereas C2 messaging focused more on parent education, proactive check-ins, and nonmedical aspects of the child's life. Four themes emerged from the platform user interviews related to C2 messaging: (1) connection to the care team, (2) efficient communication, (3) clinical uses of secure messaging, and (4) barriers to use. CONCLUSIONS: Overall, our study provides valuable insight into the benefits of secure messaging in the care of children with medical complexity. Secure messaging provided the opportunity for continued family teaching, proactive check-ins from health care providers, and casual conversations about family and child life, which contributed to PCs feeling an improved sense of connection with their child's health care team. Secure messaging can be a beneficial additional communication method to improve communication between PCs and their care team, reducing the associated burden of care coordination and ultimately enhancing the experience of care delivery. Future directions include the evaluation of secure messaging when integrated into electronic medical records, as this has the potential to work well with CTM workflow, reduce redundancy, and allow for new features of secure messaging.

The Experience of Parental Caregiving for Children With Medical Complexity.

Children with medical complexity (CMC) have complex chronic conditions with significant functional impairment, contributing to high caregiving demand. This study seeks to explore impacts of parental caregiving for CMC. Fifteen caregivers of CMC followed at a tertiary care hospital participated in semi-structured interviews. Interviews were concurrently analyzed using a qualitative description framework until thematic saturation was reached. Codes were grouped by shared concepts to clarify emergent findings. Four affected domains of parental caregiver experience with associated subthemes (in parentheses) were identified: personal (identity, physical health, mental health), family (marriage, siblings, family quality of life), social (time limitations, isolating lived experience), and financial (employment, medical costs, accessibility costs). Despite substantial challenges, caregivers identified two core determinants of personal resilience: others' support (hands-on, interpersonal, informational, material) and a positive outlook (self-efficacy, self-compassion, reframing expectations). Further research is needed to understand the unique needs and strengths of caregivers for this vulnerable population.

Housing Need Among Children With Medical Complexity: A Cross-Sectional Descriptive Study of Three Populations.

OBJECTIVE: Children with medical complexity (CMC) are hypothesized to have unique housing and accessibility needs due to their medical fragility and medical technology dependency; however, research on prevalence and types of housing need in CMC is limited. The objective was to describe housing need in families of CMC, and to compare housing need across CMC, children with one chronic condition (Type 1 diabetes; CT1D) and healthy children (HC). METHODS: This cross-sectional descriptive study assessed housing suitability, adequacy, affordability, stress, stability, and accessibility using survey methodology. Participants were caregivers of CMC, CT1D and HC at a tertiary-care pediatric hospital. The association of housing need outcomes across groups was analyzed using logistic and ordinal logistic regression models, adjusting for income, educational attainment, employment status, community type, immigration status, child age, and number of people in household. RESULTS: Four hundred ninety caregivers participated. Caregivers of CMC reported increased risk of housing-related safety concerns (aOR 3.1 [1.3-7.5]), using a common area as a sleeping area (5.6 [2.0-16.8]), reducing spending (4.6 [2.3-9.5]) or borrowing money to afford rent (2.9 [1.2-6.7]), experiencing housing stress (3.3 [1.8-6.0]), and moving or considering moving to access health/community services (15.0 [6.4-37.6]) compared to HC. CONCLUSIONS: CMC were more likely to experience multiple indicators of housing need compared to CT1D and HC even after adjusting for sociodemographic factors, suggesting an association between complexity of child health conditions and housing need. Further research and practise should consider screening for and supporting housing need in CMC.

The Experience of Housing Needs Among Families Caring for Children With Medical Complexity.

BACKGROUND AND OBJECTIVES: Caregivers of children with medical complexity (CMC) face many stressors related to their child's medical condition(s). Financial stress and its impact on housing has been reported to be a challenge among this population. However, unique housing challenges specific to CMC, including disability accommodations in the home and housing space and layout, have yet to be examined in the literature. METHODS: We conducted 20 individual semistructured interviews with parents of CMC. Interviews were recorded, coded, and analyzed by using thematic analysis to emphasize, examine, and record patterns of meaning within the data. RESULTS: Eighteen mothers and 2 fathers participated in individual interviews. Two major themes and subthemes (in parentheses) were identified: (1) the impact of health on housing (housing preferences, housing possibilities, and housing outcome as a trade-off) and (2) the impact of housing on health (health of the caregiver and health of the child). Parents had preferences regarding the location and layout of their home specific to their child's illness and medical needs. In addition, parents indicated their child's illness affected their income and home ownership status, which in turn shaped their housing possibilities. The location and layout of the family home was often the result of a trade-off between the caregiver's housing preferences and possibilities. CONCLUSIONS: Housing outcomes among CMC are often the result of a trade-off between housing preferences and possibilities, both of which are influenced by the child's health status. Policy changes targeting housing accessibility and affordability are vital to support the health of CMC.

Perspectives on team communication challenges in caring for children with medical complexity.

BACKGROUND: Children with medical complexity (CMC) require the expertise of many care providers spanning different disciplines, institutions, and settings of care. This leads to duplicate health records, breakdowns in communication, and limited opportunities to provide comprehensive, collaborative care. The objectives of this study were to explore communication challenges and solutions/recommendations from multiple perspectives including (i) parents, (ii) HCPs - hospital and community providers, and (iii) teachers of CMC with a goal of informing patient care. METHODS: This qualitative study utilized an interpretive description methodology. In-depth semi-structured interviews were conducted with parents and care team members of CMC. The interview guides targeted questions surrounding communication, coordination, access to information and roles in the health system. Interviews were conducted until thematic saturation was reached. Interviews were audio-recorded, transcribed verbatim, and coded and analyzed using thematic analysis. RESULTS: Thirty-two individual interviews were conducted involving parents (n = 16) and care team members (n = 16). Interviews revealed 2 main themes and several associated subthemes (in parentheses): (1) Communication challenges in the care of CMC (organizational policy and technology systems barriers, inadequate access to health information, and lack of partnership in care) (2) Communication solutions (shared systems that can be accessed in real-time, universal access to health information, and partnered contribution to care). CONCLUSION: Parents, HCPs, and teachers face multiple barriers to communication and information accessibility in their efforts to care for CMC. Parents and care providers in this study suggested potential strategies to improve communication including facilitating communication in real-time, universal access to health information and meaningful partnerships.

The parental experience and perceptions of blenderized tube feeding for children with medical complexity.

OBJECTIVES: Parents of children with medical complexity are often expected to implement complicated plans of care, such as enteral tube feeding, to support the health of their child. Enteral feeding can have psychosocial implications for the parent, child, and family. Blenderized tube feeding (BTF) refers to the administration of pureed food and drinks through a feeding tube. Little is known regarding parents' experiences with BTF. Therefore, the purpose of this qualitative study was to understand the lived experience of BTF from the parent's perspective. METHODS: This qualitative study was a grounded theory analysis utilizing semi-structured interviews of parents who provided at least 50% of their child's diet through BTF. Participants were recruited using purposive sampling from the Complex Care Program at a tertiary care paediatric centre. Interviews were conducted until thematic saturation was achieved. Themes were identified using constant comparative analysis of transcribed interviews. RESULTS: Parents (n=10) felt that BTF positively affected the experience of tube feeding and enhanced their child's health and wellbeing. Parents described BTF as a means of self-empowerment and a mechanism to normalize feeding and care for the entire family. Despite reporting BTF as more time consuming than formula feeding, all parents were satisfied with having made the change, and planned on continuing the diet. CONCLUSION: BTFs can improve the experience of tube feeding and positively address some of the negative psychosocial implications of enteral tube feeding, providing a sense of normalcy and control for parents caring for a child with medical complexity.

Assessment of Bereaved Caregiver Experiences of Advance Care Planning for Children With Medical Complexity.

Importance: Advance care planning (ACP) is the process of discussing values and preferences for care to help inform medical decision-making. Children with medical complexity (CMC) often have a shortened life span with an unpredictable clinical course and timing of death; however, there is a paucity of literature that describes the experience of ACP from the perspective of bereaved family caregivers of CMC. Objective: To explore the experiences of bereaved family caregivers with ACP for CMC. Design, Setting, and Participants: This qualitative study included 12 interviews with 13 bereaved family caregivers of CMC whose deaths had occurred in the 5 years before study commencement (2013-2018). Participants were recruited at a single tertiary care pediatric center; CMC were treated by the Complex Care or Long-term Ventilation clinic in Toronto, Ontario, Canada. Data were collected from July to October 2018. Thematic analysis with an inductive approach was used. Exposures: Qualitative interviews were conducted using purposive sampling of bereaved family caregivers using semistructured interviews that were recorded and transcribed. Interviews were conducted until saturation was reached. Main Outcomes and Measures: Transcripts were analyzed to create themes that characterized caregiver experiences with ACP. Results: A total of 13 family caregivers were interviewed in 12 interviews, all of whom were parents (12 [92%] women, 1 [8%] man) of a deceased child (aged 7 months to 12 years). Themes were divided in the 3 following categories, which align with the Donabedian model for health service quality: (1) structure of care, (2) ACP process, and (3) end-of-life experience. Notable subthemes for this population included the importance of accounting for parental expertise in the child's care, recurrent experiences with life-threatening events, relative shock of the timing of death, and the multiple losses that caregivers experienced. Conclusions and Relevance: In this study, parental experiences revealed that there are key aspects of the structure of the child's care, process around ACP, and end-of-life care experiences that provide important reflections on ACP that warrant future study.

Toward an Understanding of Advance Care Planning in Children With Medical Complexity.

BACKGROUND AND OBJECTIVES: Children with medical complexity (CMC) often have multiple life-limiting conditions with no unifying diagnosis and an unclear prognosis and are at high risk for morbidity and mortality. Advance care planning (ACP) conversations need to be uniquely tailored to this population. Our primary objective for this study was to develop an in-depth understanding of the ACP experiences from the perspectives of both parents and health care providers (HCPs) of CMC. METHODS: We conducted 25 semistructured interviews with parents of CMC and HCPs of various disciplines from a tertiary pediatric hospital. Interview guide questions were focused on ACP, including understanding of the definition, positive and negative experiences, and suggestions for improvement. Interviews were conducted until thematic saturation was reached. Interviews were audio recorded, transcribed verbatim, coded, and analyzed using content analysis. RESULTS: Fourteen mothers and 11 HCPs participated in individual interviews. Interviews revealed 4 major themes and several associated subthemes (in parentheses): (1) holistic mind-set, (2) discussion content (beliefs and values, hopes and goals, and quality of life), (3) communication enhancers (partnerships in shared decision-making, supportive setting, early and ongoing conversations, consistent language and practice, family readiness, provider expertise in ACP discussions, and provider comfort in ACP discussions), and (4) the ACP definition. CONCLUSIONS: Family and HCP perspectives revealed a need for family-centered ACP for CMC and their families. Our results aided the development of a family-centered framework to enhance the delivery of ACP through a holistic mind-set, thoughtful discussion content, and promoting of conversation enhancers.

Observing different model types interspersed with physical practice has no effect on consolidation or motor learning of an elbow flexion-extension task.

We compared varied model types and their potential differential effects on learning outcomes and consolidation processes when observational practice was interspersed with physical practice. Participants (N = 75) were randomly assigned to one of five groups: (1) unskilled model observation, (2) skilled model observation, (3) mixed-model observation, (4) physical practice only, and (5) no observational or physical practice (control). All were tasked with learning a waveform-matching task. With exception of the control group not involved in acquisition sessions, participants were involved in one pre-test, two acquisition sessions, four retention tests (immediate-post acquisition 1, 24hr post acquisition 1, immediate-post acquisition 2, and approximate 7-day retention), as well as an approximate 7-day transfer test. No differences were demonstrated in consolidation processes or learning outcomes as all groups showed the same pattern of retention and transfer data. Our conclusion is that motor memory processes were not impacted differentially when different models types were used in observational practice that was intermixed with physical practice for the learning of a movement pattern with low task difficulty, and thus similar learning outcomes emerged for all groups.

Abnormal mineralization of the Ts65Dn Down syndrome mouse appendicular skeleton begins during embryonic development in a Dyrk1a-independent manner.

The relationship between gene dosage imbalance and phenotypes associated with Trisomy 21, including the etiology of abnormal bone phenotypes linked to Down syndrome (DS), is not well understood. The Ts65Dn mouse model for DS exhibits appendicular skeletal defects during adolescence and adulthood but the developmental and genetic origin of these phenotypes remains unclear. It is hypothesized that the postnatal Ts65Dn skeletal phenotype originates during embryonic development and results from an increased Dyrk1a gene copy number, a gene hypothesized to play a critical role in many DS phenotypes. Ts65Dn embryos exhibit a lower percent bone volume in the E17.5 femur when compared to euploid embryos. Concomitant with gene copy number, qPCR analysis revealed a ~1.5 fold increase in Dyrk1a transcript levels in the Ts65Dn E17.5 embryonic femur as compared to euploid. Returning Dyrk1a copy number to euploid levels in Ts65Dn, Dyrk1a(+/-) embryos did not correct the trisomic skeletal phenotype but did return Dyrk1a gene transcript levels to normal. The size and protein expression patterns of the cartilage template during embryonic bone development appear to be unaffected at E14.5 and E17.5 in trisomic embryos. Taken together, these data suggest that the dosage imbalance of genes other than Dyrk1a is involved in the development of the prenatal bone phenotype in Ts65Dn embryos.

Cardiovascular development and survival during gestation in the Ts65Dn mouse model for Down syndrome.

The Ts65Dn mouse model for Down syndrome (DS) exhibits many phenotypes seen in human DS. Previous research has revealed a reduced rate of transmission of the T65Dn marker chromosome in neonates. To analyze potential fetal loss, litters from trisomic females at 10.5dpc through 14.5dpc were genotyped. No significant differences from the expected Mendelian ratio were found in transmission of T65Dn at any stage. Cardiovascular defects found in trisomic neonates are associated with formation of pharyngeal arch arteries. Vessel tracing was used to identify anomalies in 10.5dpc, 11.5dpc, and 13.5dpc embryos. Comparison of trisomic versus euploid embryos injected with India ink revealed delay and abnormality in cardiovascular development in trisomic embryos at each stage. Through the analysis of transmission rate and cardiovascular development in embryonic mice, we learn more about prenatal mortality and the origins of cardiac abnormality in the Ts65Dn mice to assist in understanding cardiovascular malformation associated with DS.

Increased male reproductive success in Ts65Dn "Down syndrome" mice.

The Ts65Dn mouse is trisomic for orthologs of about half the genes on Hsa21. A number of phenotypes in these trisomic mice parallel those in humans with trisomy 21 (Down syndrome), including cognitive deficits due to hippocampal malfunction that are sufficiently similar to human that "therapies" developed in Ts65Dn mice are making their way to human clinical trials. However, the impact of the model is limited by availability. Ts65Dn cannot be completely inbred and males are generally considered to be sterile. Females have few, small litters and they exhibit poor care of offspring, frequently abandoning entire litters. Here we report identification and selective breeding of rare fertile males from two working colonies of Ts65Dn mice. Trisomic offspring can be propagated by natural matings or by in vitro fertilization (IVF) to produce large cohorts of closely related siblings. The use of a robust euploid strain as recipients of fertilized embryos in IVF or as the female in natural matings greatly improves husbandry. Extra zygotes cultured to the blastocyst stage were used to create trisomic and euploid embryonic stem (ES) cells from littermates. We developed parameters for cryopreserving sperm from Ts65Dn males and used it to produce trisomic offspring by IVF. Use of cryopreserved sperm provides additional flexibility in the choice of oocyte donors from different genetic backgrounds, facilitating rapid production of complex crosses. This approach greatly increases the power of this important trisomic model to interrogate modifying effects of trisomic or disomic genes that contribute to trisomic phenotypes.

Characterization of the cardiac phenotype in neonatal Ts65Dn mice.

The Ts65Dn mouse is the most-studied of murine models for Down syndrome. Homology between the triplicated murine genes and those on human chromosome 21 correlates with shared anomalies of Ts65Dn mice and Down syndrome patients, including congenital heart defects. Lethality is associated with inheritance of the T65Dn chromosome, and anomalies such as right aortic arch with Kommerell's diverticulum and interrupted aortic arch were found in trisomic neonates. The incidence of gross vascular abnormalities was 17% in the trisomic population. Histological analyses revealed interventricular septal defects and broad foramen ovale, while immunohistochemistry showed abnormal muscle composition in the cardiac valves of trisomic neonates. These findings confirm that the gene imbalance present in Ts65Dn disrupts crucial pathways during cardiac development. The candidate genes for congenital heart defects that are among the 104 triplicated genes in Ts65Dn mice are, therefore, implicated in the dysregulation of normal cardiogenic pathways in this model.

The power of comparative and developmental studies for mouse models of Down syndrome.

Since the genetic basis for Down syndrome (DS) was described, understanding the causative relationship between genes at dosage imbalance and phenotypes associated with DS has been a principal goal of researchers studying trisomy 21 (Ts21). Though inferences to the gene-phenotype relationship in humans have been made, evidence linking a specific gene or region to a particular congenital phenotype has been limited. To further understand the genetic basis for DS phenotypes, mouse models with three copies of human chromosome 21 (Hsa21) orthologs have been developed. Mouse models offer access to every tissue at each stage of development, opportunity to manipulate genetic content, and ability to precisely quantify phenotypes. Numerous approaches to recreate trisomic composition and analyze phenotypes similar to DS have resulted in diverse trisomic mouse models. A murine intraspecies comparative analysis of different genetic models of Ts21 and specific DS phenotypes reveals the complexity of trisomy and important considerations to understand the etiology of and strategies for amelioration or prevention of trisomic phenotypes. By analyzing individual phenotypes in different mouse models throughout development, such as neurologic, craniofacial, and cardiovascular abnormalities, greater insight into the gene-phenotype relationship has been demonstrated. In this review we discuss how phenotype-based comparisons between DS mouse models have been useful in analyzing the relationship of trisomy and DS phenotypes.

Postnatal lethality and cardiac anomalies in the Ts65Dn Down syndrome mouse model.

The Ts65Dn mouse is a well-studied model for Down syndrome (DS). The presence of the translocation chromosome T17 16 (referred to as T65Dn) produces a trisomic dosage imbalance for over 100 genes on the distal region of mouse Chromosome 16. This dosage imbalance, with more than half of the orthologs of human Chromosome 21 (Hsa21), causes several phenotypes in the trisomic mice that are reminiscent of DS. Careful examination of neonates in a newly established Ts65Dn colony indicated high rates of postnatal lethality. Although the transmission rate for the T65Dn chromosome has been previously reported as 20%-40%, genotyping of all progeny indicates transmission at birth is near the 50% expected with Mendelian transmission and survival. Remarkably, in litters with maternal care that allowed survival of some pups, postnatal lethality occurred primarily in pups that inherited the T65Dn marker chromosome. This selective loss within 48 h of birth reduced the transmission of the marker chromosome from 49% at birth to 34% at weaning. Gross morphologic examination revealed cardiovascular anomalies, i.e., right aortic arch accompanied by septal defects, in 8.3% of the trisomic newborn cadavers examined. This is an intriguing finding because the orthologs of the DiGeorge region of HSA22, which are posited to contribute to the aortic arch abnormalities seen in trisomy 16 mice, are not triplicated in Ts65Dn mice. These new observations suggest that the Ts65Dn mouse models DS not only in its previously described phenotypes but also with elevated postnatal lethality and congenital heart malformations that may contribute to mortality.