Ferechte Razavi

Embryonic expression of the human MID1 gene and its mutations in Opitz syndrome

Opitz syndrome (G/BBB syndrome, MIM145410 and MIM300000) is a midline congenital malformation characterised by hypertelorism, hypospadias and oesophagolaryngotracheal defects leading to swallowing difficulties and a hoarse cry.1 Additional defects include cleft lip with or without cleft palate, imperforate anus, anomalies of the central nervous system (including corpus callosum agenesis or vermis agenesis and hypoplasia),2 congenital heart defects (atrial and ventricular septal defects, patent ductus arteriosus and coarctation of the aorta),3 and developmental delay in two thirds of patients. This condition is genetically heterogeneous with an X-linked recessive form mapped to Xp22.3 and at least one autosomal dominant form mapped to chromosome 22q11.2.4 Also, several patients with an autosomal Opitz syndrome have been reported with a 22q11 deletion.5,6 Recently, mutations in MID1 , a member of the B-box protein family have been identified in the X-linked form of the disease7 but the gene for the autosomal dominant form on 22q11 remains unknown. MID1 encodes a protein belonging to a novel subclass of RING, B-box, Coiled-Coil proteins characterised by a fibronectin type III motif and a C-terminal domain. Although the function of MID1 remains unknown, recent experiments have demonstrated that MID1 is a microtubule associated protein, belonging to a large multiprotein complex8,9 involved in ubiquitination through microtubules.10 MID1 association with microtubules is regulated by dynamic phosphorylation involving MAP kinase and protein phosphatase 2A that is targeted specifically to MID1 by a regulatory α4 subunit. Here, we report on six MID1 mutations in a cohort of 14 patients with Opitz syndrome and on heart and hindbrain expression of MID1 during early human development using mRNA in situ hybridisation. In addition, we investigate the contribution of chromosome X-inactivation studies to identify the X-linked form of the disease. ### Patients A total of 14 cases were included …

C5orf42 is the major gene responsible for OFD syndrome type VI

Oral-facial-digital syndrome type VI (OFD VI) is a recessive ciliopathy defined by two diagnostic criteria: molar tooth sign (MTS) and one or more of the following: (1) tongue hamartoma (s) and/or additional frenula and/or upper lip notch; (2) mesoaxial polydactyly of one or more hands or feet; (3) hypothalamic hamartoma. Because of the MTS, OFD VI belongs to the “Joubert syndrome related disorders”. Its genetic aetiology remains largely unknown although mutations in the TMEM216 gene, responsible for Joubert (JBS2) and Meckel-Gruber (MKS2) syndromes, have been reported in two OFD VI patients. To explore the molecular cause(s) of OFD VI syndrome, we used an exome sequencing strategy in six unrelated families followed by Sanger sequencing. We identified a total of 14 novel mutations in the C5orf42 gene in 9/11 families with positive OFD VI diagnostic criteria including a severe fetal case with microphthalmia, cerebellar hypoplasia, corpus callosum agenesis, polydactyly and skeletal dysplasia. C5orf42 mutations have already been reported in Joubert syndrome confirming that OFD VI and JBS are allelic disorders, thus enhancing our knowledge of the complex, highly heterogeneous nature of ciliopathies.

Mutations in tubulin genes are frequent causes of various foetal malformations of cortical development including microlissencephaly.

Complex cortical malformations associated with mutations in tubulin genes are commonly referred to as “Tubulinopathies”. To further characterize the mutation frequency and phenotypes associated with tubulin mutations, we studied a cohort of 60 foetal cases. Twenty-six tubulin mutations were identified, of which TUBA1A mutations were the most prevalent (19 cases), followed by TUBB2B (6 cases) and TUBB3 (one case). Three subtypes clearly emerged. The most frequent (n = 13) was microlissencephaly with corpus callosum agenesis, severely hypoplastic brainstem and cerebellum. The cortical plate was either absent (6/13), with a 2–3 layered pattern (5/13) or less frequently thickened (2/13), often associated with neuroglial overmigration (4/13). All cases had voluminous germinal zones and ganglionic eminences. The second subtype was lissencephaly (n = 7), either classical (4/7) or associated with cerebellar hypoplasia (3/7) with corpus callosum agenesis (6/7). All foetuses with lissencephaly and cerebellar hypoplasia carried distinct TUBA1A mutations, while those with classical lissencephaly harbored recurrent mutations in TUBA1A (3 cases) or TUBB2B (1 case). The third group was polymicrogyria-like cortical dysplasia (n = 6), consisting of asymmetric multifocal or generalized polymicrogyria with inconstant corpus callosum agenesis (4/6) and hypoplastic brainstem and cerebellum (3/6). Polymicrogyria was either unlayered or 4-layered with neuronal heterotopias (5/6) and occasional focal neuroglial overmigration (2/6). Three had TUBA1A mutations and 3 TUBB2B mutations. Foetal TUBA1A tubulinopathies most often consist in microlissencephaly or classical lissencephaly with corpus callosum agenesis, but polymicrogyria may also occur. Conversely, TUBB2B mutations are responsible for either polymicrogyria (4/6) or microlissencephaly (2/6).

Mitochondrial respiratory chain complex assembly and function during human fetal development

Oxidative phosphorylation (OXPHOS) deficiency may have early antenatal manifestations, probably related to the time course and/or tissue specificity of the disease gene expression during the embryo-fetal period. This feature hampers a fully reliable prenatal enzymological diagnosis of OXPHOS deficiency. We have studied OXPHOS in various human fetal tissues from 9 to 17 weeks of gestation. We found that the fetal respiratory chain complexes are fully assembled and functional at early stages of development in heart, liver, muscle, brain and kidney. We also observed a marked increase of respiratory chain activities and mitochondria content in postnatal compared to prenatal tissues. However, we were not able to detect obvious modification in the size, composition or activity of the various OXPHOS complexes during the second trimester of pregnancy that could account for the variations we observed in a pathological context. Therefore, we suggest that the time-dependent expression of respiratory chain deficiency either during fetal life or after birth could be related to the differential expression or regulation of the mutant proteins.

Antenatal spectrum of CHARGE syndrome in 40 fetuses with CHD7 mutations

Background CHARGE syndrome is a rare, usually sporadic disorder of multiple congenital anomalies ascribed to a CHD7 gene mutation in 60% of cases. Although the syndrome is well characterised in children, only one series of 10 fetuses with CHARGE syndrome has been reported to date. Therefore, we performed a detailed clinicopathological survey in our series of fetuses with CHD7 mutations, now extended to 40 cases. CHARGE syndrome is increasingly diagnosed antenatally, but remains challenging in many instances. Method Here we report a retrospective study of 40 cases of CHARGE syndrome with a CHD7 mutation, including 10 previously reported fetuses, in which fetal or neonatal clinical, radiological and histopathological examinations were performed. Results Conversely to postnatal studies, the proportion of males is high in our series (male to female ratio 2.6:1) suggesting a greater severity in males. Features almost constant in fetuses were external ear anomalies, arhinencephaly and semicircular canal agenesis, while intrauterine growth retardation was never observed. Finally, except for one, all other mutations identified in our antenatal series were truncating, suggesting a possible phenotype–genotype correlation. Conclusions Clinical analysis allowed us to refine the clinical description of CHARGE syndrome in fetuses, describe some novel features and set up diagnostic criteria in order to help the diagnosis of CHARGE syndrome after termination of pregnancies following the detection of severe malformations.

Lethal familial fetal akinesia sequence (FAS) with distinct neuropathological pattern: Type III lissencephaly syndrome

We report on a distinct pattern of primary central nervous system (CNS) degeneration affecting neuronal survival in the brain and spinal cord in 5 fetuses with fetal akinesia sequence (FAS). This neuropathological pattern is characteristic of a lethal entity that we propose calling type III lissencephaly syndrome. Parental consanguinity and the recurrence in sibs support a genetic cause. The mechanism of neuronal death is not yet understood; abnormal apoptosis and/or deficiency in neurotropic factors may be considered possible causes.

Immunohistochemical expression of prion protein (PrPC) in the human forebrain during development.

The cellular prion protein (PrPC) is a ubiquitous protein whose expression in the adult brain occurs mainly in synapses. We used monoclonal antibodies to study fetal and perinatal PrPC expression in the human forebrain. Double immunofluorescence and confocal microscopy with GFAP, Iba1, MAP2, doublecortin, synaptophysin, and GAP-43 were used to localize PrPC. PrPC immunoreactivity was observed in axonal tracts and fascicles from the 11th week to the end of gestation. Synapses expressed PrPC at increasing levels throughout synaptogenesis. At midgestation, a few PrPC-labeled neurons were detected in the cortical anlage and numerous ameboid and intermediate microglial cells were PrPC-positive. In contrast, at the end of gestation, microglial PrPC expression decreased to almost nothing, whereas neuronal PrPC expression increased, most notably in ischemic areas. In adults, PrPC immunoreactivity was restricted to the synaptic neuropil of the gray matter. At all ages, choroid plexus, ependymal, and endothelial cells were labeled, whereas astrocytes were only occasionally immunoreactive. In conclusion, the early expression of PrPC in the axonal field may suggest a specific role for this molecule in axonal growth during development. Moreover, PrPC may play a role in early microglial cell development.

Prenatal Cortical Hyperostosis With COL1A1 Gene Mutation

Infantile cortical hyperostosis (Caffey disease) is benign and self‐limiting when it presents near or after birth but it is usually lethal when it presents earlier. We present the clinical, ultrasonic, radiographic, and pathologic findings in an instructive case of early onset prenatal cortical hyperostosis. The pregnancy of a 21‐year‐old woman was medically terminated at 30 weeks of gestation after a diagnosis of severe osteogenesis imperfecta. Prenatal ultrasounds showed short long bones. Postmortem radiographs showed hyperostosis in long bones, ribs and mandible. The affected skeleton showed marked bony sclerosis and ballooning of the diaphyses of the long bones with periosteal sclerosis. A complete autopsy showed characteristic histologic findings of infantile cortical hyperostosis in affected bones. A missense mutation (3040C → T) in exon 41 the gene encoding the alpha 1 chain of type I collagen was found in fetus pulmonary tissue. Neither the severe form nor the mild form of prenatal cortical hyperostosis were thought to be related to collagen I mutations. Our study indicates that a heterozygous 3040C → T mutation can also be found in lethal prenatal cortical hyperostosis.

Contiguous gene deletion of TBX5 and TBX3 leads to a varible phenotype with combined features of holt-oram and ulnar-mammary syndromes

We report on a combination of congenital malformations in a mother and her fetus harboring a heterozygous deletion encompassing the TBX5 and TBX3 genes, which are disease‐causing in Holt‐Oram and ulnar‐mammary syndromes, respectively. This contiguous gene syndrome is reminiscent of Okihiro syndrome and emphasizes the importance of array‐CGH as a diagnostic tool in atypical syndromic presentations with intrafamilial variability.

Genetic testing in the context of the revision of the French law on bioethics

This article focuses on six questions raised by genetic testing in human: (1) the use of genetic tests, (2) information given to relatives of patients affected with genetic disorders, (3) prenatal and preimplantatory diagnosis for late onset genetic diseases and the use of pangenomic tests in prenatal diagnosis, (4) direct-to-consumer genetic testing, (5) population screening in the age of genomic medicine and (6) incidental findings when genetic testing are used.