ACTB Loss-of-Function Mutations Result in a Pleiotropic Developmental Disorder.

ACTB encodes ß-actin, an abundant cytoskeletal housekeeping protein. In humans, postulated gain-of-function missense mutations cause Baraitser-Winter syndrome (BRWS), characterized by intellectual disability, cortical malformations, coloboma, sensorineural deafness, and typical facial features. To date, the consequences of loss-of-function ACTB mutations have not been proven conclusively. We describe heterozygous ACTB deletions and nonsense and frameshift mutations in 33 individuals with developmental delay, apparent intellectual disability, increased frequency of internal organ malformations (including those of the heart and the renal tract), growth retardation, and a recognizable facial gestalt (interrupted wavy eyebrows, dense eyelashes, wide nose, wide mouth, and a prominent chin) that is distinct from characteristics of individuals with BRWS. Strikingly, this spectrum overlaps with that of several chromatin-remodeling developmental disorders. In wild-type mouse embryos, ß-actin expression was prominent in the kidney, heart, and brain. ACTB mRNA expression levels in lymphoblastic lines and fibroblasts derived from affected individuals were decreased in comparison to those in control cells. Fibroblasts derived from an affected individual and ACTB siRNA knockdown in wild-type fibroblasts showed altered cell shape and migration, consistent with known roles of cytoplasmic ß-actin. We also demonstrate that ACTB haploinsufficiency leads to reduced cell proliferation, altered expression of cell-cycle genes, and decreased amounts of nuclear, but not cytoplasmic, ß-actin. In conclusion, we show that heterozygous loss-of-function ACTB mutations cause a distinct pleiotropic malformation syndrome with intellectual disability. Our biological studies suggest that a critically reduced amount of this protein alters cell shape, migration, proliferation, and gene expression to the detriment of brain, heart, and kidney development.

A de novo proximal 3q29 chromosome microduplication in a patient with oculo auriculo vertebral spectrum.

Oculo auriculo vertebral spectrum (OAVS; OMIM 164210) is a clinically and genetically heterogeneous disorder originating from an abnormal development of the first and second branchial arches. Main clinical characteristics include defects of the aural, oral, mandibular, and vertebral development. Anomalies of the cardiac, pulmonary, renal, skeletal, and central nervous systems have also been described. We report on a 25-year-old male showing a spectrum of clinical manifestations fitting the OAVS diagnosis: hemifacial microsomia, asymmetric mandibular hypoplasia, preauricular pits and tags, unilateral absence of the auditory meatus, dysgenesis of the inner ear and unilateral microphthalmia. A SNP-array analysis identified a de novo previously unreported microduplication spanning 723 Kb on chromosome 3q29. This rearrangement was proximal to the 3q29 microdeletion/microduplication syndrome region, and encompassed nine genes including ATP13A3 and XXYLT1, which are involved in the organogenesis and regulation of the Notch pathway, respectively. The present observation further expands the spectrum of genomic rearrangements associated to OAVS, underlying the value of array-based studies in patients manifesting OAVS features.

Mutations in PVRL4, encoding cell adhesion molecule nectin-4, cause ectodermal dysplasia-syndactyly syndrome.

Ectodermal dysplasias form a large disease family with more than 200 members. The combination of hair and tooth abnormalities, alopecia, and cutaneous syndactyly is characteristic of ectodermal dysplasia-syndactyly syndrome (EDSS). We used a homozygosity mapping approach to map the EDSS locus to 1q23 in a consanguineous Algerian family. By candidate gene analysis, we identified a homozygous mutation in the PVRL4 gene that not only evoked an amino acid change but also led to exon skipping. In an Italian family with two siblings affected by EDSS, we further detected a missense and a frameshift mutation. PVRL4 encodes for nectin-4, a cell adhesion molecule mainly implicated in the formation of cadherin-based adherens junctions. We demonstrated high nectin-4 expression in hair follicle structures, as well as in the separating digits of murine embryos, the tissues mainly affected by the EDSS phenotype. In patient keratinocytes, mutated nectin-4 lost its capability to bind nectin-1. Additionally, in discrete structures of the hair follicle, we found alterations of the membrane localization of nectin-afadin and cadherin-catenin complexes, which are essential for adherens junction formation, and we found reorganization of actin cytoskeleton. Together with cleft lip and/or palate ectodermal dysplasia (CLPED1, or Zlotogora-Ogur syndrome) due to an impaired function of nectin-1, EDSS is the second known "nectinopathy" caused by mutations in a nectin adhesion molecule.

Case Report: A Novel Homozygous Missense Variant of FBN3 Supporting It Is a New Candidate Gene Causative of a Bardet-Biedl Syndrome-Like Phenotype.

Fibrillin proteins are extracellular matrix glycoproteins assembling into microfibrils. FBN1, FBN2, and FBN3 encode the human fibrillins and mutations in FBN1 and FBN2 cause connective tissue disorders called fibrillinopathies, affecting cardiovascular, dermal, skeletal, and ocular tissues. Recently, mutations of the less characterized fibrillin family member, FBN3, have been associated in a single family with Bardet-Biedl syndrome (BBS). Here, we report on a patient born from two first cousins and affected by developmental delay, cognitive impairment, obesity, dental and genital anomalies, and brachydactyly/syndactyly. His phenotype was very similar to that reported in the previous FBN3-mutated family and fulfilled BBS clinical diagnostic criteria, although lacking polydactyly, the most recurrent clinical feature, as the previous siblings described. A familial SNP-array and proband's WES were performed prioritizing candidate variants on the sole patient's runs of homozygosity. This analysis disclosed a novel homozygous missense variant in FBN3 (NM_032447:c.5434A>G; NP_115823:p.Ile1812Val; rs115948457), inherited from the heterozygous parents. This study further supports that FBN3 is a candidate gene for a BBS-like syndrome characterized by developmental delay, cognitive impairment, obesity, dental, genital, and skeletal anomalies. Anyway, additional studies are necessary to investigate the exact role of the gene and possible interactions between FBN3 and BBS proteins.

Production and characterization of human induced pluripotent stem cells (iPSCs) from Joubert Syndrome: CSSi001-A (2850).

Joubert Syndrome (JS) is a rare autosomal recessive or X-linked condition characterized by a peculiar cerebellar malformation, known as the molar tooth sign (MTS), associated with other neurological phenotypes and multiorgan involvement. JS is a ciliopathy, a spectrum of disorders whose causative genes encode proteins involved in the primary cilium apparatus. In order to elucidate ciliopathy-associated molecular mechanisms, human induced pluripotent stem cells (hiPSCs) were derived from a patient affected by JS carrying a homozygous missense mutation in the AHI1 gene (p.H896R) that encodes a protein named Jouberin.

6p25 interstitial deletion in two dizygotic twins with gyral pattern anomaly and speech and language disorder.

Submicroscopic 6p25 deletion is now recognized as a clinically identifiable syndrome, characterized by intellectual disability, language impairment, hearing deficit, craniofacial, ophthalmologic, cardiac, and varying central nervous system anomalies. We report on two dyzogotic twins with a maternal segregating hemizygous interstitial deletion on chromosome 6p25.1, spanning 0.9 kb; the smallest ever reported. Both had dysmorphic features (prominence of the metopic suture, synophrys, hypertelorism, down-slanting palpebral fissures, tented mouth), and a distinct brain MRI, showing a focal significant increase of the right peri-frontal subarachnoid space, with shallow sulci and a mild anomaly of the gyral pattern. Such brain anomaly has never been reported in association with del 6p25. Both propositi had a borderline-mild intellectual disability, speech and language difficulties, and behavior abnormalities. Their mother, formally tested, had a borderline cognitive impairment. Although none of the genes mapping to the deleted region are apparently related to the phenotype, LYRM4 resulted down-regulated in the cerebellar cortex of schizophrenia patients compared with controls, and Lyrm4 was down-regulated in the prefrontal cortex of mice with microdeletions in the locus syntenic to human 22q11.2 patients affected by schizophrenia. These data are in agreement with the emerging concept that similar CNVs are pathogenic in patients affected by distinct neurological diseases, and that these loci are more general risk factors for different disorders. The resemblance of our patients to those with the more extensive 6p25.1p25.3 terminal deletion suggests that the gene/s responsible for the physical phenotype should reside in the 6p25.1 genomic region.

Novel and recurrent EVC and EVC2 mutations in Ellis-van Creveld syndrome and Weyers acrofacial dyostosis.

Ellis van Creveld syndrome and Weyers acrofacial dysostosis are allelic disorders caused by mutations in EVC or EVC2 genes. We illustrate the results of direct analysis of whole EVC and EVC2 genes' coding regions in 32 unrelated families with clinical diagnosis of Ellis van Creveld syndrome and in 2 families with Weyers acrofacial dysostosis. We identified mutations in 27/32 (84%) cases with Ellis van Creveld syndrome and 2/2 cases with Weyers acrofacial dysostosis. Of the Ellis van Creveld syndrome cases, 20/27 (74%) had a mutation in EVC and 7/27 (26%) in EVC2 genes. The two subjects with Weyers acrofacial dysostosis had a heterozygous mutation in the last exon of EVC2. In total, we detected 25 independent EVC and 11 independent EVC2 mutations. Nineteen EVC mutations (19/25, 76%) and 4 EVC2 mutations (4/11, 36%) were novel. Also one EVC2 gene mutation found in Weyers acrofacial dysostosis was novel. In 5 unrelated cases with a clinical diagnosis of Ellis van Creveld syndrome, we did not find any mutation in either EVC or EVC2 genes. Current findings expand the Ellis van Creveld syndrome and Weyers acrofacial dysostosis mutation spectra, and provide further evidence that the last exon of EVC2 gene is a hot spot for Weyers acrofacial dysostosis mutations. Accordingly, EVC2 exon 22 should be analyzed with priority by mutation screening in individuals with a suspected diagnosis of Weyers acrofacial dysostosis.

16p subtelomeric duplication: a clinically recognizable syndrome.

We report on two patients with duplication of the subterminal region of chromosome 16p (dup16p) recognized by fluorescent in situ hybridization (FISH) telomere analysis, presenting with closely overlapping facial features and neurological impairment. Distinct facial anomalies included high forehead, sparse eyebrows, blepharophimosis, short nose, everted upper lip, high-arched palate, wide-spaced teeth, and cupped anteverted ears. Susceptibility to vascular anomalies, in particular pulmonary hypertension and portal cavernoma, was found in one patient. Subtelomeric analysis by FISH demonstrated a de novo duplication of the subtelomeric region of chromosome 16p and a deletion of the subtelomeric region of chromosome 4q in case 1, and duplication of the subtelomeric region of 16p and a deletion of the subtelomeric region of 21q, resulting from malsegregation of a balanced maternal traslocation t(16pter;21qter) in case 2. The extension of duplicated regions measured by array-comparative genome hybridization was about 12 Mb on 16p13.3p13.13 in case 1, and about 8.5 Mb on 16p13.3p13.2 in case 2. In conclusion, we reported a clinically recognizable disorder in two patients with dup16p. Pulmonary hypertension, vascular ring, and manifestations of vascular disruption, as terminal hypoplasia of hands and aplasia cutis, have been previously described in association with dup16p. Thus, susceptibility to pulmonary vascular disease and other vascular anomalies can be a feature of dup16p, suggesting that this subtelomeric region in some respect could be related to vascular anomalies.

Nablus mask-like facial syndrome is caused by a microdeletion of 8q detected by array-based comparative genomic hybridization.

In 2000, Teebi reported on a 4-year-old boy with a distinctive pattern of malformation, which he termed the "Nablus mask-like facial syndrome" (OMIM# 608156). Characterization of this syndrome has been difficult because of the paucity of patients described in the medical literature and its unknown etiology and pathogenesis. We present two patients with Nablus mask-like facial syndrome who both display a microdeletion in the 8q21-8q22 region detected by array-based comparative genomic hybridization. Patient 1, a boy, has a distinct facial appearance characterized by severe blepharophimosis, tight-appearing glistening facial skin, sparse and unruly hair, a flat and broad nose, and distinctive ears that are triangular in shape with prominent antihelices. He also demonstrates camptodactyly, contractures, unusual dentition, cryptorchidism, mild developmental delay, and a happy demeanor. Patient 2, a girl with a strikingly similar phenotype, was previously described in a report by Salpietro et al. 2003. She has distinctive ears, dental anomalies, and developmental delay. The etiology of her pattern of malformation was not identified at that time. Although high-resolution chromosome and subtelomeric FISH analyses were normal, array-based comparative genomic hybridization revealed an approximately 4 Mb deletion involving the 8q21.3-8q22.1 region in both patients. This region encompasses a number of genes that may contribute to this unique phenotype. These results demonstrate a chromosomal microdeletion as the etiology of Nablus mask-like facial syndrome and emphasize the diagnostic utility of array-based comparative genomic hybridization in the evaluation of multiple malformation syndromes of previously unrecognized causation.