RLIM Is a Candidate Dosage-Sensitive Gene for Individuals with Varying Duplications of Xq13, Intellectual Disability, and Distinct Facial Features.

Interpretation of the significance of maternally inherited X chromosome variants in males with neurocognitive phenotypes continues to present a challenge to clinical geneticists and diagnostic laboratories. Here we report 14 males from 9 families with duplications at the Xq13.2-q13.3 locus with a common facial phenotype, intellectual disability (ID), distinctive behavioral features, and a seizure disorder in two cases. All tested carrier mothers had normal intelligence. The duplication arose de novo in three mothers where grandparental testing was possible. In one family the duplication segregated with ID across three generations. RLIM is the only gene common to our duplications. However, flanking genes duplicated in some but not all the affected individuals included the brain-expressed genes NEXMIF, SLC16A2, and the long non-coding RNA gene FTX. The contribution of the RLIM-flanking genes to the phenotypes of individuals with different size duplications has not been fully resolved. Missense variants in RLIM have recently been identified to cause X-linked ID in males, with heterozygous females typically having normal intelligence and highly skewed X chromosome inactivation. We detected consistent and significant increase of RLIM mRNA and protein levels in cells derived from seven affected males from five families with the duplication. Subsequent analysis of MDM2, one of the targets of the RLIM E3 ligase activity, showed consistent downregulation in cells from the affected males. All the carrier mothers displayed normal RLIM mRNA levels and had highly skewed X chromosome inactivation. We propose that duplications at Xq13.2-13.3 including RLIM cause a recognizable but mild neurocognitive phenotype in hemizygous males.

Copy number variant discrepancy resolution using the ClinGen dosage sensitivity map results in updated clinical interpretations in ClinVar.

Conflict resolution in genomic variant interpretation is a critical step toward improving patient care. Evaluating interpretation discrepancies in copy number variants (CNVs) typically involves assessing overlapping genomic content with focus on genes/regions that may be subject to dosage sensitivity (haploinsufficiency (HI) and/or triplosensitivity (TS)). CNVs containing dosage sensitive genes/regions are generally interpreted as "likely pathogenic" (LP) or "pathogenic" (P), and CNVs involving the same known dosage sensitive gene(s) should receive the same clinical interpretation. We compared the Clinical Genome Resource (ClinGen) Dosage Map, a publicly available resource documenting known HI and TS genes/regions, against germline, clinical CNV interpretations within the ClinVar database. We identified 251 CNVs overlapping known dosage sensitive genes/regions but not classified as LP or P; these were sent back to their original submitting laboratories for re-evaluation. Of 246 CNVs re-evaluated, an updated clinical classification was warranted in 157 cases (63.8%); no change was made to the current classification in 79 cases (32.1%); and 10 cases (4.1%) resulted in other types of updates to ClinVar records. This effort will add curated interpretation data into the public domain and allow laboratories to focus attention on more complex discrepancies.

Disruption of the ASTN2/TRIM32 locus at 9q33.1 is a risk factor in males for autism spectrum disorders, ADHD and other neurodevelopmental phenotypes.

Rare copy number variants (CNVs) disrupting ASTN2 or both ASTN2 and TRIM32 have been reported at 9q33.1 by genome-wide studies in a few individuals with neurodevelopmental disorders (NDDs). The vertebrate-specific astrotactins, ASTN2 and its paralog ASTN1, have key roles in glial-guided neuronal migration during brain development. To determine the prevalence of astrotactin mutations and delineate their associated phenotypic spectrum, we screened ASTN2/TRIM32 and ASTN1 (1q25.2) for exonic CNVs in clinical microarray data from 89 985 individuals across 10 sites, including 64 114 NDD subjects. In this clinical dataset, we identified 46 deletions and 12 duplications affecting ASTN2. Deletions of ASTN1 were much rarer. Deletions near the 3' terminus of ASTN2, which would disrupt all transcript isoforms (a subset of these deletions also included TRIM32), were significantly enriched in the NDD subjects (P = 0.002) compared with 44 085 population-based controls. Frequent phenotypes observed in individuals with such deletions include autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), speech delay, anxiety and obsessive compulsive disorder (OCD). The 3'-terminal ASTN2 deletions were significantly enriched compared with controls in males with NDDs, but not in females. Upon quantifying ASTN2 human brain RNA, we observed shorter isoforms expressed from an alternative transcription start site of recent evolutionary origin near the 3' end. Spatiotemporal expression profiling in the human brain revealed consistently high ASTN1 expression while ASTN2 expression peaked in the early embryonic neocortex and postnatal cerebellar cortex. Our findings shed new light on the role of the astrotactins in psychopathology and their interplay in human neurodevelopment.

Further Defining the Role of the Laboratory Genetic Counselor.

Laboratory genetic counseling is becoming increasingly common as a result of increased laboratory services and genetic testing menus, as well as growing job responsibilities. Christian et al. (2012) provided the first quantitative data regarding the roles of the laboratory-based genetic counselor (LBGC) finding that two of the most prevalent roles are as customer liaisons and communicators of test results. The goal of the present study was to further delineate the role of the LBGC by addressing specific tasks that LBGCs are involved with on a day-to-day basis. A survey was designed to expand upon themes identified in the Christian et al. (2012) study by querying specific tasks performed in several categories of potential LBGC job duties. An invitation for LBGCs to participate was distributed via email to the membership of the National Society of Genetic Counselors (NSGC) and the Canadian Association of Genetic Counsellors (CAGC). We identified 121 genetic counselors who primarily work in the laboratory setting or whose job role includes a laboratory component. Almost all respondents performed customer liaison/case coordination (95 %), and interpretation and result reporting (88 %). The most frequently performed tasks within these categories involved addressing questions from clients, making phone calls with genetic testing results, obtaining clinical or family history information for results interpretation, and composing case-specific interpretations for unique results and/or obtaining literature references to support interpretations. The study results also point to trends of expanding roles in sales and marketing, variant interpretation and management responsibilities. Results of this study may be useful to further define the full scope of practice of LBGCs, aid in the development of new LBGC positions and expand current positions to include roles related to test development, research, and student supervision. It may also aid in curriculum updates for training programs to increase exposure to LBGC roles.

The phenotype spectrum of X-linked ichthyosis identified by chromosomal microarray.

BACKGROUND: Steroid sulfatase (STS) gene disruption causes X-linked ichthyosis (XLI). Interrogating the entire genome through chromosomal microarray (CMA), a test primarily used to screen patients with noncutaneous congenital anomalies, may detect STS deletions incidentally. OBJECTIVE: We sought to determine the variability of skin features associated with STS deletions diagnosed through CMA and to compare these findings with XLI cases reported in the literature and recognized in a dermatology clinic. METHODS: Male patients with an STS deletion were identified from 23,172 consecutive postnatal blood samples tested with CMA at Mayo Clinic. A comparison group of male patients with biochemically confirmed XLI was ascertained in the dermatology clinic. The available patient medical records, skin histopathology, and photographs were evaluated and a literature search of patients with XLI was conducted. RESULTS: Children whose diagnosis was made incidentally through CMA had milder skin phenotypes, including dryness or eczema, or both, and did not manifest the polygonal or "dirty" scale described as typical of XLI in the literature. LIMITATIONS: The small sample size, limited clinical information, and assessment by nondermatologists in a subset of cases may have influenced the results. CONCLUSION: STS deletions may cause a milder skin phenotype than the typical presentation of XLI.

Comorbidity and Severity in Childhood Apraxia of Speech: A Retrospective Chart Review.

PURPOSE: The purpose of this study was to investigate comorbidity prevalence and patterns in childhood apraxia of speech (CAS) and their relationship to severity. METHOD: In this retroactive cross-sectional study, medical records for 375 children with CAS (M age = 4;9 [years;months], SD = 2;9) were examined for comorbid conditions. The total number of comorbid conditions and the number of communication-related comorbidities were regressed on CAS severity as rated by speech-language pathologists during diagnosis. The relationship between CAS severity and the presence of four common comorbid conditions was also examined using ordinal or multinomial regressions. RESULTS: Overall, 83 children were classified with mild CAS; 35, with moderate CAS; and 257, with severe CAS. Only one child had no comorbidities. The average number of comorbid conditions was 8.4 (SD = 3.4), and the average number of communication-related comorbidities was 5.6 (SD = 2.2). Over 95% of children had comorbid expressive language impairment. Children with comorbid intellectual disability (78.1%), receptive language impairment (72.5%), and nonspeech apraxia (37.3%; including limb, nonspeech oromotor, and oculomotor apraxia) were significantly more likely to have severe CAS than children without these comorbidities. However, children with comorbid autism spectrum disorder (33.6%) were no more likely to have severe CAS than children without autism. CONCLUSIONS: Comorbidity appears to be the rule, rather than the exception, for children with CAS. Comorbid intellectual disability, receptive language impairment, and nonspeech apraxia confer additional risk for more severe forms of CAS. Findings are limited by being from a convenience sample of participants but inform future models of comorbidity. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.22096622.

Clinical Validation of Tagmentation-Based Genome Sequencing for Germline Disorders.

Genome sequencing (GS) is a powerful clinical tool used for the comprehensive diagnosis of germline disorders. GS library preparation typically involves mechanical DNA fragmentation, end repair, and bead-based library size selection followed by adapter ligation, which can require a large amount of input genomic DNA. Tagmentation using bead-linked transposomes can simplify the library preparation process and reduce the DNA input requirement. Here we describe the clinical validation of tagmentation-based PCR-free GS as a clinical test for rare germline disorders. Compared with the Genome-in-a-Bottle Consortium benchmark variant sets, GS had a recall >99.7% and a precision of 99.8% for single nucleotide variants and small insertion-deletions. GS also exhibited 100% sensitivity for clinically reported sequence variants and the copy number variants examined. Furthermore, GS detected mitochondrial sequence variants above 5% heteroplasmy and showed reliable detection of disease-relevant repeat expansions and SMN1 homozygous loss. Our results indicate that while lowering DNA input requirements and reducing library preparation time, GS enables uniform coverage across the genome as well as robust detection of various types of genetic alterations. With the advantage of comprehensive profiling of multiple types of genetic alterations, GS is positioned as an ideal first-tier diagnostic test for germline disorders.

Offering Prenatal Screening in the Age of Genomic Medicine: A Practical Guide.

AIMS: In September, 2015, Mayo Clinic convened a panel of national thought leaders on prenatal screening, medical genetics, and obstetrics and gynecology practice. RESULTS: During the 2-day symposium, participants discussed the implications of the shift toward broader prenatal screening using cell-free placental DNA in maternal serum (cfDNA screening). Key topics included challenges around the pace of change in the prenatal screening market, uncertainty around reimbursement, meeting the need for patient counseling, and potential challenges in interpreting and returning cfDNA screening results. INNOVATION: Here, we describe the challenges discussed and offer clinical recommendations for practices who are working to meet them. CONCLUSION: As the spread of prenatal genetic screening continues, providers will increasingly need to update their practice to accommodate new screening modalities.