Discovering a new part of the phenotypic spectrum of Coffin-Siris syndrome in a fetal cohort.

PURPOSE: Genome-wide sequencing is increasingly being performed during pregnancy to identify the genetic cause of congenital anomalies. The interpretation of prenatally identified variants can be challenging and is hampered by our often limited knowledge of prenatal phenotypes. To better delineate the prenatal phenotype of Coffin-Siris syndrome (CSS), we collected clinical data from patients with a prenatal phenotype and a pathogenic variant in one of the CSS-associated genes. METHODS: Clinical data was collected through an extensive web-based survey. RESULTS: We included 44 patients with a variant in a CSS-associated gene and a prenatal phenotype; 9 of these patients have been reported before. Prenatal anomalies that were frequently observed in our cohort include hydrocephalus, agenesis of the corpus callosum, hypoplastic left heart syndrome, persistent left vena cava, diaphragmatic hernia, renal agenesis, and intrauterine growth restriction. Anal anomalies were frequently identified after birth in patients with ARID1A variants (6/14, 43%). Interestingly, pathogenic ARID1A variants were much more frequently identified in the current prenatal cohort (16/44, 36%) than in postnatal CSS cohorts (5%-9%). CONCLUSION: Our data shed new light on the prenatal phenotype of patients with pathogenic variants in CSS genes.

P63-related disorders: Dermatological characteristics in 22 patients.

In P63-related ectodermal dysplasias (ED), the clinical characteristics focus on extra-cutaneous manifestations. The dermatological phenotype remains incompletely characterized. We report the dermatological features of 22 patients carrying a TP63 mutation. Erosions, erythroderma and pigmentary anomalies are characteristics of P63-related ED. Our data suggest that patients might be classified into two major P63-related disorders: AEC and EEC. RHS and ADULT represent mild AEC and EEC forms, respectively.

Mutations in KIAA0586 Cause Lethal Ciliopathies Ranging from a Hydrolethalus Phenotype to Short-Rib Polydactyly Syndrome.

KIAA0586, the human ortholog of chicken TALPID3, is a centrosomal protein that is essential for primary ciliogenesis. Its disruption in animal models causes defects attributed to abnormal hedgehog signaling; these defects include polydactyly and abnormal dorsoventral patterning of the neural tube. Here, we report homozygous mutations of KIAA0586 in four families affected by lethal ciliopathies ranging from a hydrolethalus phenotype to short-rib polydactyly. We show defective ciliogenesis, as well as abnormal response to SHH-signaling activation in cells derived from affected individuals, consistent with a role of KIAA0586 in primary cilia biogenesis. Whereas centriolar maturation seemed unaffected in mutant cells, we observed an abnormal extended pattern of CEP290, a centriolar satellite protein previously associated with ciliopathies. Our data show the crucial role of KIAA0586 in human primary ciliogenesis and subsequent abnormal hedgehog signaling through abnormal GLI3 processing. Our results thus establish that KIAA0586 mutations cause lethal ciliopathies.

Novel de novo ZBTB20 mutations in three cases with Primrose syndrome and constant corpus callosum anomalies.

Corpus callosum (CC) is the major brain commissure connecting homologous areas of cerebral hemispheres. CC anomalies (CCAs) are the most frequent brain anomalies leading to variable neurodevelopmental outcomes making genetic counseling difficult in the absence of a known etiology that might inform the prognosis. Here, we used whole exome sequencing, and a targeted capture panel of syndromic CCA known causal and candidate genes to screen a cohort of 64 fetuses with CCA observed upon autopsy, and 34 children with CCA and intellectual disability. In one fetus and two patients, we identified three novel de novo mutations in ZBTB20, which was previously shown to be causal in Primrose syndrome. In addition to CCA, all cases presented with additional features of Primrose syndrome including facial dysmorphism and macrocephaly or megalencephaly. All three variations occurred within two out of the five zinc finger domains of the transcriptional repressor ZBTB20. Through homology modeling, these variants are predicted to result in local destabilization of each zinc finger domain suggesting subsequent abnormal repression of ZBTB20 target genes. Neurohistopathological analysis of the fetal case showed abnormal regionalization of the hippocampal formation as well as a reduced density of cortical upper layers where originate most callosal projections. Here, we report novel de novo ZBTB20 mutations in three independent cases with characteristic features of Primrose syndrome including constant CCA. Neurohistopathological findings in fetal case corroborate the observed key role of ZBTB20 during hippocampal and neocortical development. Finally, this study highlights the crucial role of ZBTB20 in CC development in human.

Genetic and phenotypic dissection of 1q43q44 microdeletion syndrome and neurodevelopmental phenotypes associated with mutations in ZBTB18 and HNRNPU.

Subtelomeric 1q43q44 microdeletions cause a syndrome associating intellectual disability, microcephaly, seizures and anomalies of the corpus callosum. Despite several previous studies assessing genotype-phenotype correlations, the contribution of genes located in this region to the specific features of this syndrome remains uncertain. Among those, three genes, AKT3, HNRNPU and ZBTB18 are highly expressed in the brain and point mutations in these genes have been recently identified in children with neurodevelopmental phenotypes. In this study, we report the clinical and molecular data from 17 patients with 1q43q44 microdeletions, four with ZBTB18 mutations and seven with HNRNPU mutations, and review additional data from 37 previously published patients with 1q43q44 microdeletions. We compare clinical data of patients with 1q43q44 microdeletions with those of patients with point mutations in HNRNPU and ZBTB18 to assess the contribution of each gene as well as the possibility of epistasis between genes. Our study demonstrates that AKT3 haploinsufficiency is the main driver for microcephaly, whereas HNRNPU alteration mostly drives epilepsy and determines the degree of intellectual disability. ZBTB18 deletions or mutations are associated with variable corpus callosum anomalies with an incomplete penetrance. ZBTB18 may also contribute to microcephaly and HNRNPU to thin corpus callosum, but with a lower penetrance. Co-deletion of contiguous genes has additive effects. Our results confirm and refine the complex genotype-phenotype correlations existing in the 1qter microdeletion syndrome and define more precisely the neurodevelopmental phenotypes associated with genetic alterations of AKT3, ZBTB18 and HNRNPU in humans.

Clinical, genetic and neuropathological findings in a series of 138 fetuses with a corpus callosum malformation.

BACKGROUND: Corpus callosum malformation (CCM) is the most frequent brain malformation observed at birth. Because CCM is a highly heterogeneous condition, the prognosis of fetuses diagnosed prenatally remains uncertain, making prenatal counseling difficult. METHODS AND RESULTS: We evaluated retrospectively a total of 138 fetuses, 117 with CCM observed on prenatal imaging examination, and 21 after postmortem autopsy. On ultrasound and/or magnetic resonance imaging, CCM was either isolated (N = 40) or associated with other neurological (N = 57) or extra cerebral findings (N = 21/20, respectively). RESULTS: Most fetuses (N = 132) remained without a diagnosis at the time of pregnancy termination. This emphasizes the need to establish a neuropathological classification and to perform a genomic screening using comparative genomic hybridization. A neuropathological examination performed on 138 cases revealed a spectrum of CCMs, classified as follows: agenesis of corpus callosum (55), CC hypoplasia (30), CC dysmorphism (24), and CCM associated with a malformation of cortical development (29). Of interest, after fetopathological examination, only 16/40 malformations were classified as isolated, highlighting the importance of the autopsy following termination of pregnancy. Among the 138 cases, the underlying etiology was found in 46 cases: diabetes (one case), cytomegalovirus infection (one case), 23 chromosome abnormalities, and 21 mendelian conditions. CONCLUSION: In our series of 138 cases of CCM, prenatal and postmortem examinations identified a variety of genetic causes. However, no diagnosis could be established in 67% of cases. The classification based on the underlying neurodevelopmental defects paves the way for further genetic studies and genotype-phenotype correlations.

TCTN3 mutations cause Mohr-Majewski syndrome.

Orofaciodigital syndromes (OFDSs) consist of a group of heterogeneous disorders characterized by abnormalities in the oral cavity, face, and digits and associated phenotypic abnormalities that lead to the delineation of 13 OFDS subtypes. Here, by a combined approach of homozygozity mapping and exome ciliary sequencing, we identified truncating TCTN3 mutations as the cause of an extreme form of OFD associated with bone dysplasia, tibial defect, cystic kidneys, and brain anomalies (OFD IV, Mohr-Majewski syndrome). Analysis of 184 individuals with various ciliopathies (OFD, Meckel, Joubert, and short rib polydactyly syndromes) led us to identify four additional truncating TCTN3 mutations in unrelated fetal cases with overlapping Meckel and OFD IV syndromes and one homozygous missense mutation in a family with Joubert syndrome. By exploring roles of TCTN3 in human ciliary related functions, we found that TCTN3 is necessary for transduction of the sonic hedgehog (SHH) signaling pathway, as revealed by abnormal processing of GLI3 in patient cells. These results are consistent with the suggested role of its murine ortholog, which forms a complex at the ciliary transition zone with TCTN1 and TCTN2, both of which are also implicated in the transduction of SHH signaling. Overall, our data show the involvement of the transition zone protein TCTN3 in the regulation of the key SHH signaling pathway and that its disruption causes a severe form of ciliopathy, combining features of Meckel and OFD IV syndromes.

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.

Novel KIF7 mutations extend the phenotypic spectrum of acrocallosal syndrome.

BACKGROUND: Acrocallosal syndrome (ACLS) is a rare recessive disorder characterised by corpus callosum agenesis or hypoplasia, craniofacial dysmorphism, duplication of the hallux, postaxial polydactyly, and severe mental retardation. Recently, we identified mutations in KIF7, a key component of the Sonic hedgehog pathway, as being responsible for this syndrome. METHODS: We sequenced KIF7 in five suspected ACLS cases, one fetus and four patients, based on facial dysmorphism and brain anomalies. RESULTS: Seven mutations were identified at the KIF7 locus in these five cases, six of which are novel. We describe the first four compound heterozygous cases. In all patients, the diagnosis was suspected based on the craniofacial features, despite the absence of corpus callosum anomaly in one and of polydactyly in another. Hallux duplication was absent in 4/5 cases. CONCLUSIONS: These results show that ACLS has a variable expressivity and can be diagnosed even in the absence of the two major features, namely polydactyly or agenesis or hypoplasia of the corpus callosum. Facial dysmorphism with hypertelorism and prominent forehead in all the cases, as well as vermis dysgenesis with brainstem anomalies (molar tooth sign), strongly indicated the diagnosis. KIF7 should be tested in less typical patients in whom craniofacial features are suggestive of ACLS.

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.

Bothnian Palmoplantar Keratoderma: Further Delineation of the Associated Phenotype.

Bothnian palmoplantar keratoderma (PPKB, MIM600231) is an autosomal dominant form of diffuse non-epidermolytic PPK characterized by spontaneous yellowish-white PPK associated with a spongy appearance after water-immersion. It is due to AQP5 heterozygous mutations. We report four patients carrying a novel AQP5 heterozygous mutation (c.125T>A; p.(Ile42Asn)), and belonging to the same French family. Early palmoplantar swelling (before one year of age), pruritus and hyperhidrosis were constant. The PPK was finally characterized as transgrediens, non-progrediens, diffuse PPK with a clear delineation between normal and affected skin. The cutaneous modifications at water-immersion test, "hand-in-the-bucket sign", were significantly evident after 3 to 6 min of immersion in the children and father, respectively. AQP5 protein is expressed in eccrine sweat glands (ESG), salivary and airway submucosal glands. In PPKB, gain of function mutations seem to widen the channel diameter of ESG and increase water movement. Thus, swelling seems to be induced by hypotonicity with water entrance into cells, while hyperhidrosis is the result of an increased cytosolic calcium concentration.

Corrigendum: TALPID3/KIAA0586 Regulates Multiple Aspects of Neuromuscular Patterning During Gastrointestinal Development in Animal Models and Human.

[This corrects the article DOI: 10.3389/fnmol.2021.757646.].

Prenatal-onset of congenital neuronal ceroid lipofuscinosis with a novel CTSD mutation.

BACKGROUND: Neuronal ceroid lipofuscinoses (NCLs) form a clinically and genetically heterogeneous group of inherited neurodegenerative disorders that share common neuropathological features. Although they are the first cause of neurodegenerative disorders in children, their congenital forms are rarely documented. They are classically due to mutations in the CTSD gene (the CLN10 disease). Affected newborns usually present severe microcephaly, seizures and respiratory failure leading to death within the first postnatal days or weeks. CASES: We report on two siblings, in which exome sequencing identified a novel homozygous CTSD variant. The first sib presented at birth with seizures, rapidly progressive postnatal microcephaly and visual deficiency related to retinal dysfunction. Progressive neurological deterioration leads to death at the age of 24 months. Cathepsin D activity was reduced in the cultured fibroblasts of this patient. The second sib, a fetus of 36 weeks of gestation, was delivered after pregnancy termination for brain abnormalities (in accordance with French Legislation) suggesting a recurrence of the disease. Fetal postmortem examination disclosed neuropathological features consistent with NCL. CONCLUSIONS: Congenital NCL related to CTSD mutations is a neuronal storage disorder that produces in the developing brain diffuse neurodegeneration and white matter atrophy resulting in a progressive and rapidly lethal microcephaly.

TALPID3/KIAA0586 Regulates Multiple Aspects of Neuromuscular Patterning During Gastrointestinal Development in Animal Models and Human.

TALPID3/KIAA0586 is an evolutionary conserved protein, which plays an essential role in protein trafficking. Its role during gastrointestinal (GI) and enteric nervous system (ENS) development has not been studied previously. Here, we analyzed chicken, mouse and human embryonic GI tissues with TALPID3 mutations. The GI tract of TALPID3 chicken embryos was shortened and malformed. Histologically, the gut smooth muscle was mispatterned and enteric neural crest cells were scattered throughout the gut wall. Analysis of the Hedgehog pathway and gut extracellular matrix provided causative reasons for these defects. Interestingly, chicken intra-species grafting experiments and a conditional knockout mouse model showed that ENS formation did not require TALPID3, but was dependent on correct environmental cues. Surprisingly, the lack of TALPID3 in enteric neural crest cells (ENCC) affected smooth muscle and epithelial development in a non-cell-autonomous manner. Analysis of human gut fetal tissues with a KIAA0586 mutation showed strikingly similar findings compared to the animal models demonstrating conservation of TALPID3 and its necessary role in human GI tract development and patterning.

A neuropathological study of novel RTTN gene mutations causing a familial microcephaly with simplified gyral pattern.

BACKGROUND: The RTTN gene encodes Rotatin, a large centrosomal protein involved in ciliary functions. RTTN mutations have been reported in seven families and are associated with two phenotypes: polymicrogyria associated with seizures and primary microcephaly associated with primordial dwarfism. CASE: A targeted exome sequencing of morbid genes causing cerebral malformations identified novel RTTN compound heterozygous mutations in a family where three pregnancies were terminated because a severe fetal microcephaly was diagnosed. An autopsy performed on the second sib showed moderate growth restriction and a microcephaly with simplified gyral pattern. The histopathological study discovered a malformed cortical plate. CONCLUSIONS: The present study confirms the involvement of RTTN gene mutations in microcephaly with simplified gyral pattern and describes the observed abnormal neuropathological findings.

In utero ultrasound diagnosis of corpus callosum agenesis leading to the identification of orofaciodigital type 1 syndrome in female fetuses.

BACKGROUND: OFD1 syndrome is a rare ciliopathy inherited on a dominant X-linked mode, typically lethal in males in the first or second trimester of pregnancy. It is characterized by oral cavity and digital anomalies possibly associated with cerebral and renal signs. Its prevalence is between 1/250,000 and 1/50,000 births. It is due to heterozygous mutations of OFD1 and mutations are often de novo (75%). Familial forms show highly variable phenotypic expression. OFD1 encodes a protein involved in centriole growth, distal appendix formation, and ciliogenesis. CASES: We report the investigation of three female fetuses in which corpus callosum agenesis was detected by ultrasound during the second trimester of pregnancy. In all three fetuses, fetopathological examination allowed the diagnosis of OFD1 syndrome, which was confirmed by molecular analysis. CONCLUSIONS: To our knowledge, these are the first case reports of antenatal diagnosis of OFD1 syndrome in the absence of familial history, revealed following detection of agenesis of the corpus callosum. They highlight the impact of fetal examination following termination of pregnancy for brain malformations. They also highlight the contribution of ciliary genes to corpus callosum development.

Fetal Cerebral Ventricular Dilatation: Etiopathogenic Study of 130 Observations.

BACKGROUND: Fetal cerebral ventricular dilatation (CVD) is a common abnormal prenatal finding that often predicts a poor prognosis. The etiology involves both genetic and nongenetic factors with diverse pathogenic mechanisms. We describe the neuropathological features of CVD in a large cohort of fetuses. The goals are to determine the physiopathological mechanisms and etiologies. METHODS: We retrospectively analyzed a series of 130 fetuses examined at the Necker University Hospital following termination of pregnancy between January 2000 and December 2014. Chiari II and Dandy-Walker malformations were excluded from our study population. Karyotype and/or array comparative genomic hybridization were performed in all cases. Targeted Sanger sequencing or next generation sequencing were carried out in 34 and 5 cases, respectively. RESULTS: We distinguished four groups of pathological entities: (1) midbrain/hindbrain patterning defects (54 cases, 42%), mainly related to aqueduct of Sylvius anomalies (atresia or stenosis); (2) cerebral cytoarchitectonic disorders (16 cases, 12%), essentially resulting from arachnoidal neuroglial ectopia; (3) hemorrhagic and perfusion failure (42 cases, 32%); and (4) nonspecific CVD (18 cases, 14%), without apparent obstruction, cortical malformation, or clastic injury. Although the pathogenic mechanisms of CVD were identified in 86% of cases, the causes, both acquired and genetic, were recognized in 21% of cases only. CONCLUSION: The neuropathological analysis is a powerful tool in the diagnosis of the fetal CVD pathogenic mechanisms and to identify homogeneous groups. The paucity of molecular diagnosis, notably in the major groups of midbrain/hindbrain patterning defects and hemorrhagic and perfusion failure, highlights the needs of future research to improve our current knowledge on CVD causes. Birth Defects Research 109:1586-1595, 2017. © 2017 Wiley Periodicals, Inc.