COVID-19 and Down’s syndrome: are we heading for a disaster?

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Down syndrome and infertility: what support should we provide?

International audienceDown syndrome (DS) is the most common genetic disease at birth; on average, it affects 1 in 700 newborns. The syndrome features cognitive impairment, susceptibility to certain diseases, and (in some cases) congenital malformations. Improvements in medical care for people with DS have led to an increase in life expectancy. Furthermore, the systematic provision of specific support during childhood improves cognitive function and autonomy in adulthood. Consequently, patients and their families are now seeking the same rights as healthy people. Access to procreation is an emerging debate. The presumption of infertility in DS is based on a few old studies. Down syndrome appears to cause spermatogenesis defects in men and premature menopause in women. When assisted reproductive technology makes it possible to solve these problems, the question of fertility in DS must be addressed. Without entering into highly controversial ethical considerations related to parenthood for people with DS, we reviewed the literature on fertility in DS and tried to specify the associated genetic risk

Prenatal diagnosis of 2q13 duplications: The crucial role of the family survey in genetic counseling on novel copy number variations

International audienceIn recent years, the introduction of novel genome analysis technologies (such as array comparative genomic hybridization) has enabled the prenatal diagnosis of various recurrent copy number variations (CNVs). Some of these CNVs have been linked to a greater susceptibility of developmental and neuropsychiatric disorders; for example, recurrent duplication at the 2q13 locus is associated with developmental delay, dysmorphism and intellectual disability. However, this CNV has low penetrance and variable clinical expressivity. It also can be observed in healthy controls and can be transmitted by unaffected parents, making genetic counseling especially challenging. Here, we report on the inheritance of a 2q13 duplication in an asymptomatic family; the case highlights the role of the family survey in genetic counseling with regard to novel CNVs diagnosed before birth

Metabolic Diseases and Down Syndrome: How Are They Linked Together?

International audienceDown syndrome is a genetic disorder caused by the presence of a third copy of chromosome 21, associated with intellectual disabilities. Down syndrome is associated with anomalies of both the nervous and endocrine systems. Over the past decades, dramatic advances in Down syndrome research and treatment have helped to extend the life expectancy of these patients. Improved life expectancy is obviously a positive outcome, but it is accompanied with the need to address previously overlooked complications and comorbidities of Down syndrome, including obesity and diabetes, in order to improve the quality of life of Down syndrome patients. In this focused review, we describe the associations between Down syndrome and comorbidities, obesity and diabetes, and we discuss the understanding of proposed mechanisms for the association of Down syndrome with metabolic disorders. Drawing molecular mechanisms through which Type 1 diabetes and Type 2 diabetes could be linked to Down syndrome could allow identification of novel drug targets and provide therapeutic solutions to limit the development of metabolic and cognitive disorders

Prenatal treatment with preimplantation factor improves early postnatal neurogenesis and cognitive impairments in a mouse model of Down syndrome

International audienceDown syndrome (DS) is a genetic disease characterized by a supernumerary chromosome 21. Intellectual deficiency (ID) is one of the most prominent features of DS. Central nervous system defects lead to learning disabilities, motor and language delays, and memory impairments. At present, a prenatal treatment for the ID in DS is lacking. Subcutaneous administration of synthetic preimplantation factor (sPIF, a peptide with a range of biological functions) in a model of severe brain damage has shown neuroprotective and anti-inflammatory properties by directly targeting neurons and microglia. Here, we evaluated the effect of PIF administration during gestation and until weaning on Dp(16)1Yey mice (a mouse model of DS). Possible effects at the juvenile stage were assessed using behavioral tests and molecular and histological analyses of the brain. To test the influence of perinatal sPIF treatment at the adult stage, hippocampus-dependent memory was evaluated on postnatal day 90. Dp(16)1Yey pups showed significant behavioral impairment, with impaired neurogenesis, microglial cell activation and a low microglial cell count, and the deregulated expression of genes linked to neuroinflammation and cell cycle regulation. Treatment with sPIF restored early postnatal hippocampal neurogenesis, with beneficial effects on astrocytes, microglia, inflammation, and cell cycle markers. Moreover, treatment with sPIF restored the level of DYRK1A, a protein that is involved in cognitive impairments in DS. In line with the beneficial effects on neurogenesis, perinatal treatment with sPIF was associated with an improvement in working memory in adult Dp(16)1Yey mice. Perinatal treatment with sPIF might be an option for mitigating cognitive impairments in people with DS

DYRK1A Overexpression in Mice Downregulates the Gonadotropic Axis and Disturbs Early Stages of Spermatogenesis

International audienceDown syndrome (DS) is the most common chromosomal disorder. It is responsible for intellectual disability (ID) and several medical conditions. Although men with DS are thought to be infertile, some spontaneous paternities have been reported. The few studies of the mechanism of infertility in men with DS are now dated. Recent research in zebrafish has indicated that overexpression of DYRK1A (the protein primarily responsible for ID in DS) impairs gonadogenesis at the embryonic stage. To better ascertain DYRK1A’s role in infertility in DS, we investigated the effect of DYRK1A overexpression in a transgenic mouse model. We found that overexpression of DYRK1A impairs fertility in transgenic male mice. Interestingly, the mechanism in mice differs slightly from that observed in zebrafish but, with disruption of the early stages of spermatogenesis, is similar to that seen in humans. Unexpectedly, we observed hypogonadotropic hypogonadism in the transgenic mice

MPC2 variants disrupt mitochondrial pyruvate metabolism and cause an early-onset mitochondriopathy

International audiencePyruvate is an essential metabolite produced by glycolysis in the cytosol and must be transported across the inner mitochondrial membrane into the mitochondrial matrix, where it is oxidized to fuel mitochondrial respiration. Pyruvate import is performed by the mitochondrial pyruvate carrier (MPC), a hetero-oligomeric complex composed by interdependent subunits MPC1 and MPC2. Pathogenic variants in the MPC1 gene disrupt mitochondrial pyruvate uptake and oxidation and cause autosomal-recessive early-onset neurological dysfunction in humans. The present work describes the first pathogenic variants in MPC2 associated with human disease in four patients from two unrelated families. In the first family, patients presented with antenatal developmental abnormalities and harboured a homozygous c.148T>C (p.Trp50Arg) variant. In the second family, patients that presented with infantile encephalopathy carried a missense c.2T>G (p.Met1?) variant disrupting the initiation codon. Patient-derived skin fibroblasts exhibit decreased pyruvate-driven oxygen consumption rates with normal activities of the pyruvate dehydrogenase complex and mitochondrial respiratory chain and no defects in mitochondrial content or morphology. Re-expression of wild-type MPC2 restored pyruvate-dependent respiration rates in patient-derived fibroblasts. The discovery of pathogenic variants in MPC2 therefore broadens the clinical and genetic landscape associated with inborn errors in pyruvate metabolism

2p25.3 microduplications involving MYT1L: further phenotypic characterization through an assessment of 16 new cases and a literature review

International audienceMicroduplications involving the MYT1L gene have mostly been described in series of patients with isolated schizophrenia. However, few reports have been published, and the phenotype has still not been well characterized. We sought to further characterize the phenotypic spectrum of this condition by describing the clinical features of patients with a pure 2p25.3 microduplication that includes all or part of MYT1L. We assessed 16 new patients with pure 2p25.3 microduplications recruited through a French national collaboration (n = 15) and the DECIPHER database (n = 1). We also reviewed 27 patients reported in the literature. For each case, we recorded clinical data, the microduplication size, and the inheritance pattern. The clinical features were variable and included developmental and speech delays (33%), autism spectrum disorder (ASD, 23%), mild-to-moderate intellectual disability (ID, 21%), schizophrenia (23%), or behavioral disorders (16%). Eleven patients did not have an obvious neuropsychiatric disorder. The microduplications ranged from 62.4 kb to 3.8 Mb in size and led to duplication of all or part of MYT1L; seven of these duplications were intragenic. The inheritance pattern was available for 18 patients: the microduplication was inherited in 13 cases, and all parents but one had normal phenotype. Our comprehensive review and expansion of the phenotypic spectrum associated with 2p25.3 microduplications involving MYT1L should help clinicians to better assess, counsel and manage affected individuals. MYT1L microduplications are characterized by a spectrum of neuropsychiatric phenotypes with incomplete penetrance and variable expressivity, which are probably due to as-yet unknown genetic and nongenetic modifiers

DNA ligase IV deficiency: Immunoglobulin class deficiency depends on the genotype

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Antenatal ultrasound features of isolated recurrent copy number variation in 7q11.23 (Williams syndrome and 7q11.23 duplication syndrome)

International audienceObjective: We aimed to gather fetal cases carrying a 7q11.23 copy number variation (CNV) and collect precise clinical data to broaden knowledge of antenatal features in these syndromes.Methods: We retrospectively recruited unrelated cases with 7q11.23 deletion, known as Williams-Beuren syndrome (WBS), or 7q11.23 duplication who had prenatal ultrasound findings. We collected laboratory and clinical data, fetal ultrasound, cardiac ultrasound and fetal autopsy reports from 18 prenatal diagnostic centers throughout France.Results: 40 fetuses with WBS were collected and the most common features were intra-uterine growth retardation (IUGR) (70.0%, 28/40), cardiovascular defects (30.0%, 12/40), polyhydramnios (17.5%, 7/40) and protruding tongue (15.0%, 6/40). Fetal autopsy reports were available for 11 cases and were compared with ultrasound prenatal features. Four cases of fetuses with 7q11.23 microduplication were collected and prenatal ultrasound signs were variable and often isolated.Conclusion: This work strengthens the fact that 7q11.23 CNVs are associated with a broad spectrum of antenatal presentations. IUGR and cardiovascular defects were the most frequent ultrasound signs. By reporting the biggest series of antenatal WBS, we aim to better delineate distinctive signs in fetuses with 7q11.23 CNVs