Non-Mammalian Models for Understanding Neurological Defects in RASopathies.

RASopathies, a group of neurodevelopmental congenital disorders stemming from mutations in the RAS/MAPK pathway, present a unique opportunity to delve into the intricacies of complex neurological disorders. Afflicting approximately one in a thousand newborns, RASopathies manifest as abnormalities across multiple organ systems, with a pronounced impact on the central and peripheral nervous system. In the pursuit of understanding RASopathies' neurobiology and establishing phenotype-genotype relationships, in vivo non-mammalian models have emerged as indispensable tools. Species such as Danio rerio, Drosophila melanogaster, Caenorhabditis elegans, Xenopus species and Gallus gallus embryos have proven to be invaluable in shedding light on the intricate pathways implicated in RASopathies. Despite some inherent weaknesses, these genetic models offer distinct advantages over traditional rodent models, providing a holistic perspective on complex genetics, multi-organ involvement, and the interplay among various pathway components, offering insights into the pathophysiological aspects of mutations-driven symptoms. This review underscores the value of investigating the genetic basis of RASopathies for unraveling the underlying mechanisms contributing to broader neurological complexities. It also emphasizes the pivotal role of non-mammalian models in serving as a crucial preliminary step for the development of innovative therapeutic strategies.

PTEN hamartoma tumor syndrome: Clinical and genetic characterization in pediatric patients.

OBJECTIVE: The aim of this study was to provide a full characterization of a cohort of 11 pediatric patients diagnosed with PTEN hamartoma tumor syndrome (PHTS). PATIENTS AND METHODS: Eleven patients with genetic diagnostic of PHTS were recruited between February 2019 and April 2023. Clinical, imaging, demographic, and genetic data were retrospectively collected from their hospital medical history. RESULTS: Regarding clinical manifestations, macrocephaly was the leading sign, present in all patients. Frontal bossing was the most frequent dysmorphism. Neurological issues were present in most patients. Dental malformations were described for the first time, being present in 27% of the patients. Brain MRI showed anomalies in 57% of the patients. No tumoral lesions were present at the time of the study. Regarding genetics, 72% of the alterations were in the tensin-type C2 domain of PTEN protein. We identified four PTEN genetic alterations for the first time. CONCLUSIONS: PTEN mutations appear with a wide variety of clinical signs and symptoms, sometimes associated with phenotypes which do not fit classical clinical diagnostic criteria for PHTS. We recommend carrying out a genetic study to establish an early diagnosis in children with significant macrocephaly. This facilitates personalized monitoring and enables anticipation of potential PHTS-related complications.

Lessons from mouse models in the impact of risk factors on the genesis of childhood B-cell leukemia.

B-cell acute lymphoblastic leukemia (B-ALL) stands as the primary contributor to childhood cancer-related mortality on a global scale. The development of the most conventional forms of this disease has been proposed to be conducted by two different steps influenced by different types of risk factors. The first step is led by a genetic insult that is presumably acquired before birth that transforms a healthy cell into a preleukemic one, which is maintained untransformed until the second step takes place. This necessary next step to leukemia development will be triggered by different risk factors to which children are exposed after birth. Murine models that recap the stepwise progression of B-ALL have been instrumental in identifying environmental and genetic factors that contribute to disease risk. Recent evidence from these models has demonstrated that specific environmental risk factors, such as common infections or gut microbiome dysbiosis, induce immune stress, driving the transformation of preleukemic cells, and harboring genetic alterations, into fully transformed leukemic cells. Such models serve as valuable tools for investigating the mechanisms underlying preleukemic events and can aid in the development of preventive approaches for leukemia in child. Here, we discuss the existing knowledge, learned from mouse models, of the impact of genetic and environmental risk factors on childhood B-ALL evolution and how B-ALL prevention could be reached by interfering with preleukemic cells.

Adaptation, reliability and validity of health-related quality of life questionnaires: Disabkids chronic and specific diabetes disease in children and adolescents with diabetes mellitus type 1.

INTRODUCTION: It is recommended to periodically evaluate the health-related quality of life (HRQoL) in children and adolescents with type 1 diabetes mellitus (DM1). Despite this, no specific paediatric HRQoL instrument for DM1 has been validated in Spanish. OBJECTIVES: Multicentre, prospective descriptive study in children and adolescents with DM1 with the aim of carrying out cross-cultural adaptation to Spanish and evaluating the reliability and validity of the DISABKIDS chronic disease and diabetes-specific HRQoL questionnaires, using reverse translation. MATERIAL AND METHODS: Sociodemographic variables were compiled together with the most recent capillary glycated haemoglobin (HbA1c) value and HRQoL questionnaires were handed out to 200 Spanish children and adolescents with DM1 aged between 8 and 18 years of age under evaluation in 12 different hospitals. RESULTS: The mean score on the HRQoL questionnaire (patient version) for chronic disease was 80.32 (13.66), being significantly lower (P = .04) in patients with a shorter duration of the disease (≤5 years): 78.34 (13.70) vs. 82.60 (13.36). The mean score of the DM1-specific modules was: 60.81 (16.23) for disease impact and 65.59 (26.19) for treatment impact. The mean HbA1c value was 7.08 (0.79), with no differences (P > .05) noted in the mean score of the HRQoL instruments in patients with HbA1c ≤7% vs. HbA1c >7%. The Cronbach α value varied between 0.72 and 0.90. CONCLUSIONS: The Spanish versions of the DISABKIDS HRQoL instruments meet the proposed objectives of semantic equivalence and internal consistency, making it possible to periodically assess HRQoL in these patients. The good average glycaemic control presented by the patients may explain why no difference was found in the HRQoL instruments based on the HbA1c value.

Immune stress suppresses innate immune signaling in preleukemic precursor B-cells to provoke leukemia in predisposed mice.

The initial steps of B-cell acute lymphoblastic leukemia (B-ALL) development usually pass unnoticed in children. Several preclinical studies have shown that exposure to immune stressors triggers the transformation of preleukemic B cells to full-blown B-ALL, but how this takes place is still a longstanding and unsolved challenge. Here we show that dysregulation of innate immunity plays a driving role in the clonal evolution of pre-malignant Pax5+/- B-cell precursors toward leukemia. Transcriptional profiling reveals that Myd88 is downregulated in immune-stressed pre-malignant B-cell precursors and in leukemic cells. Genetic reduction of Myd88 expression leads to a significant increase in leukemia incidence in Pax5+/-Myd88+/- mice through an inflammation-dependent mechanism. Early induction of Myd88-independent Toll-like receptor 3 signaling results in a significant delay of leukemia development in Pax5+/- mice. Altogether, these findings identify a role for innate immunity dysregulation in leukemia, with important implications for understanding and therapeutic targeting of the preleukemic state in children.

Expanding the phenotypic spectrum of TRAPPC11-related muscular dystrophy: 25 Roma individuals carrying a founder variant.

BACKGROUND: Limb-girdle muscular dystrophies (LGMD) are a heterogeneous group of genetically determined muscle disorders. TRAPPC11-related LGMD is an autosomal-recessive condition characterised by muscle weakness and intellectual disability. METHODS: A clinical and histopathological characterisation of 25 Roma individuals with LGMD R18 caused by the homozygous TRAPPC11 c.1287+5G>A variant is reported. Functional effects of the variant on mitochondrial function were investigated. RESULTS: The c.1287+5G>A variant leads to a phenotype characterised by early onset muscle weakness, movement disorder, intellectual disability and elevated serum creatine kinase, which is similar to other series. As novel clinical findings, we found that microcephaly is almost universal and that infections in the first years of life seem to act as triggers for a psychomotor regression and onset of seizures in several individuals with TRAPPC11 variants, who showed pseudometabolic crises triggered by infections. Our functional studies expanded the role of TRAPPC11 deficiency in mitochondrial function, as a decreased mitochondrial ATP production capacity and alterations in the mitochondrial network architecture were detected. CONCLUSION: We provide a comprehensive phenotypic characterisation of the pathogenic variant TRAPPC11 c.1287+5G>A, which is founder in the Roma population. Our observations indicate that some typical features of golgipathies, such as microcephaly and clinical decompensation associated with infections, are prevalent in individuals with LGMD R18.

Normal range for acid-labile subunit in paediatric patients in Spain and its association with age, sex, pubertal stage and other growth factors.

INTRODUCTION: The acid-labile subunit (ALS) plays an important role in the endocrine effects of insulin-like growth factors (IGFs) on target tissues. Historically, it has attracted limited attention. The aim of our study was to describe the normal range of ALS in healthy children and its association with other growth factors. PATIENTS AND METHODS: We designed a cross-sectional descriptive study. We collected data on age, height, body mass index, gestational age, anthropometry at birth and serum levels of ALS, IGF1 and IGFBP3 in healthy children aged 2-15 years with a normal height. The levels of ALS, IGF1 and IGFBP3 were measured by ELISA. We fitted GAMLSS normalization models to standardize the variables. RESULTS: Samples were collected from 446 children. In prepubertal children, the levels of ALS, IGF1 and IGFBP3 were positively correlated in both sexes and with age (P < .01). We found significant differences in the levels of ALS, IGF1 and IGFBP3 and the IGF1/IGFBP3 molar ratio between the sexes and higher levels in pubertal boys (P < .01). We generated normal probability plots for each sex for each of the components of the ternary complex and for the IGF1/IGFBP3 and IGFBP3/ALS molar ratios. In addition, we extracted equations from the models for the calculation of z-scores for age and sex. CONCLUSIONS: This study may contribute age- and sex-specific reference values for IGF1, IGFBP3 and ALS levels and IGF1/IGFBP3 and IGFBP3/ALS ratios in Spanish children and suggests an association between age, sex, and pubertal stage.

Clinical description, molecular delineation and genotype-phenotype correlation in 340 patients with KBG syndrome: addition of 67 new patients.

BACKGROUND: KBG syndrome is a highly variable neurodevelopmental disorder and clinical diagnostic criteria have changed as new patients have been reported. Both loss-of-function sequence variants and large deletions (copy number variations, CNVs) involving ANKRD11 cause KBG syndrome, but no genotype-phenotype correlation has been reported. METHODS: 67 patients with KBG syndrome were assessed using a custom phenotypical questionnaire. Manifestations present in >50% of the patients and a 'phenotypical score' were used to perform a genotype-phenotype correlation in 340 patients from our cohort and the literature. RESULTS: Neurodevelopmental delay, macrodontia, triangular face, characteristic ears, nose and eyebrows were the most prevalentf (eatures. 82.8% of the patients had at least one of seven main comorbidities: hearing loss and/or otitis media, visual problems, cryptorchidism, cardiopathy, feeding difficulties and/or seizures. Associations found included a higher phenotypical score in patients with sequence variants compared with CNVs and a higher frequency of triangular face (71.1% vs 42.5% in CNVs). Short stature was more frequent in patients with exon 9 variants (62.5% inside vs 27.8% outside exon 9), and the prevalence of intellectual disability/attention deficit hyperactivity disorder/autism spectrum disorder was lower in patients with the c.1903_1907del variant (70.4% vs 89.4% other variants). Presence of macrodontia and comorbidities were associated with larger deletion sizes and hand anomalies with smaller deletions. CONCLUSION: We present a detailed phenotypical description of KBG syndrome in the largest series reported to date of 67 patients, provide evidence of a genotype-phenotype correlation between some KBG features and specific ANKRD11 variants in 340 patients, and propose updated clinical diagnostic criteria based on our findings.

Childhood B-Cell Preleukemia Mouse Modeling.

Leukemia is the most usual childhood cancer, and B-cell acute lymphoblastic leukemia (B-ALL) is its most common presentation. It has been proposed that pediatric leukemogenesis occurs through a "multi-step" or "multi-hit" mechanism that includes both in utero and postnatal steps. Many childhood leukemia-initiating events, such as chromosomal translocations, originate in utero, and studies so far suggest that these "first-hits" occur at a far higher frequency than the incidence of childhood leukemia itself. The reason why only a small percentage of the children born with such preleukemic "hits" will develop full-blown leukemia is still a mystery. In order to better understand childhood leukemia, mouse modeling is essential, but only if the multistage process of leukemia can be recapitulated in the model. Therefore, mouse models naturally reproducing the "multi-step" process of childhood B-ALL will be essential to identify environmental or other factors that are directly linked to increased risk of disease.

Transient Inhibition of the JAK/STAT Pathway Prevents B-ALL Development in Genetically Predisposed Mice.

Preventing development of childhood B-cell acute lymphoblastic leukemia (B-ALL), a disease with devastating effects, is a longstanding and unsolved challenge. Heterozygous germline alterations in the PAX5 gene can lead to B-ALL upon accumulation of secondary mutations affecting the JAK/STAT signaling pathway. Preclinical studies have shown that this malignant transformation occurs only under immune stress such as exposure to infectious pathogens. Here we show in Pax5+/- mice that transient, early-life administration of clinically relevant doses of ruxolitinib, a JAK1/2 inhibitor, significantly mitigates the risk of B-ALL following exposure to infection; 1 of 29 animals treated with ruxolitinib developed B-ALL versus 8 of 34 untreated mice. Ruxolitinib treatment preferentially targeted Pax5+/- versus wild-type B-cell progenitors and exerted unique effects on the Pax5+/- B-cell progenitor transcriptional program. These findings provide the first in vivo evidence for a potential strategy to prevent B-ALL development. SIGNIFICANCE: JAK/STAT inhibition suppresses tumorigenesis in a B-ALL-susceptible mouse model, presenting a novel approach to prevent B-ALL onset.

The Second Oncogenic Hit Determines the Cell Fate of ETV6-RUNX1 Positive Leukemia.

ETV6-RUNX1 is almost exclusively associated with childhood B-cell acute lymphoblastic leukemia (B-ALL), but the consequences of ETV6-RUNX1 expression on cell lineage decisions during B-cell leukemogenesis are completely unknown. Clinically silent ETV6-RUNX1 preleukemic clones are frequently found in neonatal cord blood, but few carriers develop B-ALL as a result of secondary genetic alterations. The understanding of the mechanisms underlying the first transforming steps could greatly advance the development of non-toxic prophylactic interventions. Using genetic lineage tracing, we examined the capacity of ETV6-RUNX1 to instruct a malignant phenotype in the hematopoietic lineage by cell-specific Cre-mediated activation of ETV6-RUNX1 from the endogenous Etv6 gene locus. Here we show that, while ETV6-RUNX1 has the propensity to trigger both T- and B-lymphoid malignancies, it is the second hit that determines tumor cell identity. To instigate leukemia, both oncogenic hits must place early in the development of hematopoietic/precursor cells, not in already committed B-cells. Depending on the nature of the second hit, the resulting B-ALLs presented distinct entities that were clearly separable based on their gene expression profiles. Our findings give a novel mechanistic insight into the early steps of ETV6-RUNX1+ B-ALL development and might have major implications for the potential development of ETV6-RUNX1+ B-ALL prevention strategies.

Clinical response to growth hormone in children with intrauterine growth retardation without catch-up growth in Castilla y León (Spain). / Respuesta clínica al tratamiento con hormona de crecimiento en niños con retraso de crecimiento intrauterino sin recuperación posnatal de talla en Castilla y León.

INTRODUCTION AND OBJECTIVES: Growth hormone (rhGH) is used in children with intrauterine growth retardation without catch-up growth. The Advisory Committee of Castilla y León was implemented in 2010 to watch for consistent application of the criteria for using rhGH. The aim is to assess anthropometric and clinical changes in children treated with growth hormone. PATIENTS AND METHODS: A retrospective, longitudinal study of patients diagnosed with intrauterine growth retardation without catch-up growth in Castilla y León since 2010 who have received treatment for at least 3 years. Changes in anthropometric, clinical, and laboratory parameters were assessed. RESULTS: Forty-three children with a mean age of 6.06 years (58.14%<5 years) were enrolled and treated with a mean dose of 0.038mg/kg/day. A significant increase was seen in height (-3.05 to -1.58SD). Both weight and BMI (14.51 to 15.80kg/m2) increased throughout the study. Growth rate peaked during the first year of treatment (0.74SD). IGF-1 levels increased throughout the study (99.96 to 392.88ng/mL). There were significant increases in glycosylated hemoglobin levels in the first year, and in basal blood glucose and insulin levels during the second year. The LDL/HDL ratio decreased during the study period (1.70 to 1.50). CONCLUSION: Treatment with rhGH promotes growth in children with intrauterine growth retardation. Peak effect occurs in the first 12 months of treatment, and is greater when growth hormone is started before the age of 5 years.

Heterozygous aggrecan variants are associated with short stature and brachydactyly: Description of 16 probands and a review of the literature.

OBJECTIVE: Mutations in the aggrecan gene (ACAN) have been identified in two autosomal dominant skeletal dysplasias, spondyloepiphyseal dysplasia, Kimberley type (SEDK), and osteochondritis dissecans, as well as in a severe recessive dysplasia, spondyloepimetaphyseal dysplasia, aggrecan type. Next-generation sequencing (NGS) has aided the identification of heterozygous ACAN mutations in individuals with short stature, minor skeletal defects and mild facial dysmorphisms, some of whom have advanced bone age (BA), poor pubertal spurt and early growth cessation as well as precocious osteoarthritis. DESIGN AND METHODS: This study involves clinical and genetic characterization of 16 probands with heterozygous ACAN variants, 14 with short stature and mild skeletal defects (group 1) and two with SEDK (group 2). Subsequently, we reviewed the literature to determine the frequency of the different clinical characteristics in ACAN-positive individuals. RESULTS: A total of 16 ACAN variants were located throughout the gene, six pathogenic mutations and 10 variants of unknown significance (VUS). Interestingly, brachydactyly was observed in all probands. Probands from group 1 with a pathogenic mutation tended to be shorter, and 60% had an advanced BA compared to 0% in those with a VUS. A higher incidence of coxa valga was observed in individuals with a VUS (37% vs 0%). Nevertheless, other features were present at similar frequencies. CONCLUSIONS: ACAN should be considered as a candidate gene in patients with short stature and minor skeletal defects, particularly those with brachydactyly, and in patients with spondyloepiphyseal dysplasia. It is also important to note that advanced BA and osteoarticular complications are not obligatory conditions for aggrecanopathies/aggrecan-associated dysplasias.

Autosomal Recessive Hypercholesterolemia: Long-Term Cardiovascular Outcomes.

BACKGROUND: Autosomal recessive hypercholesterolemia (ARH) is a rare lipid disorder characterized by premature atherosclerotic cardiovascular disease (ASCVD). There are sparse data for clinical management and cardiovascular outcomes in ARH. OBJECTIVES: Evaluation of changes in lipid management, achievement of low-density lipoprotein cholesterol (LDL-C) goals and cardiovascular outcomes in ARH. METHODS: Published ARH cases were identified by electronic search. All corresponding authors and physicians known to treat these patients were asked to provide follow-up information, using a standardized protocol. RESULTS: We collected data for 52 patients (28 females, 24 males; 31.1 ± 17.1 years of age; baseline LDL-C: 571.9 ± 171.7 mg/dl). During a mean follow-up of 14.1 ± 7.3 years, there was a significant increase in the use of high-intensity statin and ezetimibe in combination with lipoprotein apheresis; in 6 patients, lomitapide was also added. Mean LDL-C achieved at nadir was 164.0 ± 85.1 mg/dl (-69.6% from baseline), with a better response in patients taking lomitapide (-88.3%). Overall, 23.1% of ARH patients reached LDL-C of <100 mg/dl. During follow-up, 26.9% of patients had incident ASCVD, and 11.5% had a new diagnosis of aortic valve stenosis (absolute risk per year of 1.9% and 0.8%, respectively). No incident stroke was observed. Age (≥30 years) and the presence of coronary artery disease at diagnosis were the major predictors of incident ASCVD. CONCLUSIONS: Despite intensive treatment, LDL-C in ARH patients remains far from targets, and this translates into a poor long-term cardiovascular prognosis. Our data highlight the importance of an early diagnosis and treatment and confirm the fact that an effective treatment protocol for ARH is still lacking.

Autosomal recessive hypercholesterolemia in Spain.

BACKGROUND AND AIMS: Autosomal recessive hypercholesterolemia (ARH) is a very rare disease, caused by mutations in LDL protein receptor adaptor 1 (LDLRAP1). It is characterized by high levels of low-density lipoprotein cholesterol (LDL-C) and increased risk of premature cardiovascular disease. We aimed to characterize ARH in Spain. METHODS: Data were collected from the Dyslipidemia Registry of the Spanish Atherosclerosis Society. A literature search was performed up to June 2017, and all diagnostic genetic studies for familial hypercholesterolemia of Spain were reviewed. RESULTS: Seven patients with ARH were identified, 6 true homozygous and one compound heterozygous with a novel mutation: c.[863C>T];p.[Ser288Leu]. High genetic heterogeneity was found in this cohort. True homozygous subjects for LDLRAP1 have more severe phenotypes than the compound heterozygous patient, but similar to patients with homozygous familial hypercholesterolemia (HoFH). Cardiovascular disease was present in 14% of the ARH patients. LDL-C under treatment was above 185 mg/dl and the response to PCSK9 inhibitors was heterogeneous. Finally, the estimated prevalence in Spain is very low, with just 1 case per 6.5 million people. CONCLUSIONS: ARH is a very rare disease in Spain, showing high genetic heterogeneity, similarly high LDL-C concentrations, but lower incidence of ASCVD than HoFH.

Clinical and molecular characteristics of homozygous familial hypercholesterolemia patients: Insights from SAFEHEART registry.

BACKGROUND: Homozygous familial hypercholesterolemia (HoFH) is a rare genetic disorder associated with very high levels of cholesterol, accelerated atherosclerosis and very premature death, often secondary to occlusion of the coronary ostia by supravalvular atheroma in untreated individuals. OBJECTIVE: To describe molecular and clinical characteristics of HoFH enrolled at SAFEHEART registry and to evaluate the role of the type of mutation in clinical expression. METHODS: SAFEHEART is a registry of molecularly defined familial hypercholesterolemia patients. A standardized phone call is made every year for the follow-up. Patients with confirmed HoFH were selected. Molecular and clinical characteristics were analyzed. RESULTS: Thirty-four HoFH patients (27 true HoFH, 4 compound heterozygous familial hypercholesterolemia, and 3 autosomal recessive hypercholesterolemia) have been enrolled in the period 2004-2015. Twenty different mutations in LDLR gene have been detected. Sixteen patients carry defective mutations (DMs), and 15 carry null mutations (NMs). Only patients with NMs met low-density lipoprotein cholesterol (LDL-C) criteria for clinical diagnosis. Patients with NMs had higher untreated LDL-C levels (P < .0001), more aortic valve stenosis (P < .05), and lower age at first cardiovascular event (P < .05) compared to patients with DMs. In the follow-up, 1 liver transplant patient died and 3 cases underwent revascularization procedures. Eight cases started LDL apheresis and 1 case had a liver transplant. CONCLUSIONS: HoFH phenotypic expression is highly variable. These patients have high atherosclerotic coronary artery disease risk including aortic valve stenosis and do not achieve the LDL-C treatment goals with standard therapy.

[Turner syndrome: Study of 42 cases]. / Síndrome de Turner: análisis de 42 casos.

BACKGROUND AND OBJECTIVE: Turner syndrome (TS) is characterized by short stature, gonadal dysgenesis, and total or partial loss of X chromosome. PATIENTS AND METHODS: A historical cohorts study of patients with TS≤18 years old followed up in public hospitals in Castilla y Leon was undertaken. RESULTS: Forty-two female patients were included (prenatal diagnosis 11.9%, neonatal diagnosis 14.3%) with current median age 11.9±4.2 years. Short stature was the reason for consultation in 87.1%. Total monosomy of X chromosome was present in 40.5%. The most frequently associated comorbidity was opthalmological (50%), with heart defects in 23.8%. Ninety-three percent were treated with growth hormone (GH), mean age at the beginning of treatment was 7.43±3.4 years and mean height standard deviation was -2.84±1.08. Final height was reached in 10 patients only (mean final height 151.47±6.09cm). Chronological age of puberty induction was 13.2±0.94 years (bone age 12.47±1.17 years). CONCLUSIONS: Short stature was an important clinical sign for the diagnosis of TS, accompanied in some cases by other findings, with good response to GH treatment.