Weill-Marchesani syndrome: natural history and genotype-phenotype correlations from 18 news cases and review of literature.

BACKGROUND: Weill-Marchesani syndrome (WMS) belongs to the group of acromelic dysplasias, defined by short stature, brachydactyly and joint limitations. WMS is characterised by specific ophthalmological abnormalities, although cardiovascular defects have also been reported. Monoallelic variations in FBN1 are associated with a dominant form of WMS, while biallelic variations in ADAMTS10, ADAMTS17 and LTBP2 are responsible for a recessive form of WMS. OBJECTIVE: Natural history description of WMS and genotype-phenotype correlation establishment. MATERIALS AND METHODS: Retrospective multicentre study and literature review. INCLUSION CRITERIA: clinical diagnosis of WMS with identified pathogenic variants. RESULTS: 61 patients were included: 18 individuals from our cohort and 43 patients from literature. 21 had variants in ADAMTS17, 19 in FBN1, 19 in ADAMTS10 and 2 in LTBP2. All individuals presented with eye anomalies, mainly spherophakia (42/61) and ectopia lentis (39/61). Short stature was present in 73% (from -2.2 to -5.5 SD), 10/61 individuals had valvulopathy. Regarding FBN1 variants, patients with a variant located in transforming growth factor (TGF)-ß-binding protein-like domain 5 (TB5) domain were significantly smaller than patients with FBN1 variant outside TB5 domain (p=0.0040). CONCLUSION: Apart from the ophthalmological findings, which are mandatory for the diagnosis, the phenotype of WMS seems to be more variable than initially described, partially explained by genotype-phenotype correlation.

Agonists of prostaglandin E2 receptors as potential first in class treatment for nephronophthisis and related ciliopathies.

Nephronophthisis (NPH) is an autosomal recessive tubulointerstitial nephropathy belonging to the ciliopathy disorders and known as the most common cause of hereditary end-stage renal disease in children. Yet, no curative treatment is available. The major gene, NPHP1, encodes a protein playing key functions at the primary cilium and cellular junctions. Using a medium-throughput drug-screen in NPHP1 knockdown cells, we identified 51 Food and Drug Administration-approved compounds by their ability to alleviate the cellular phenotypes associated with the loss of NPHP1; 11 compounds were further selected for their physicochemical properties. Among those compounds, prostaglandin E1 (PGE1) rescued ciliogenesis defects in immortalized patient NPHP1 urine-derived renal tubular cells, and improved ciliary and kidney phenotypes in our NPH zebrafish and Nphp1 knockout mouse models. Furthermore, Taprenepag, a nonprostanoid prostaglandin E2 receptor agonist, alleviated the severe retinopathy observed in Nphp1−/− mice. Finally, comparative transcriptomics allowed identification of key signaling pathways downstream PGE1, including cell cycle progression, extracellular matrix, adhesion, or actin cytoskeleton organization. In conclusion, using in vitro and in vivo models, we showed that prostaglandin E2 receptor agonists can ameliorate several of the pleotropic phenotypes caused by the absence of NPHP1; this opens their potential as a first therapeutic option for juvenile NPH-associated ciliopathies.

Impairment of chondrogenesis and microfibrillar network in Adamtsl2 deficiency.

Mutations in the a disintegrin and metalloproteinase with thrombospondin motif-like 2 ( ADAMTSL2) gene are responsible for the autosomal recessive form of geleophysic dysplasia, which is characterized by short stature, short extremities, and skeletal abnormalities. However, the exact function of ADAMTSL2 is unknown. To elucidate the role of this protein in skeletal development, we generated complementary knockout (KO) mouse models with either total or chondrocyte Adamtsl2 deficiency. We observed that the Adamtsl2 KO mice displayed skeletal abnormalities reminiscent of the human phenotype. Adamtsl2 deletion affected the growth plate formation with abnormal differentiation and proliferation of chondrocytes. In addition, a TGF-ß signaling impairment in limbs lacking Adamtsl2 was demonstrated. Further investigations revealed that Adamtsl2 KO chondrocytes failed to establish a microfibrillar network composed by fibrillin1 and latent TGF-ß binding protein 1 fibrils. Chondrocyte Adamtsl2 KO mice also exhibited dwarfism. These studies uncover the function of Adamtsl2 in the maintenance of the growth plate ECM by modulating the microfibrillar network.-Delhon, L., Mahaut, C., Goudin, N., Gaudas, E., Piquand, K., Le Goff, W., Cormier-Daire, V., Le Goff, C. Impairment of chondrogenesis and microfibrillar network in Adamtsl2 deficiency.

Myhre and LAPS syndromes: clinical and molecular review of 32 patients.

Myhre syndrome is characterized by short stature, brachydactyly, facial features, pseudomuscular hypertrophy, joint limitation and hearing loss. We identified SMAD4 mutations as the cause of Myhre syndrome. SMAD4 mutations have also been identified in laryngotracheal stenosis, arthropathy, prognathism and short stature syndrome (LAPS). This study aimed to review the features of Myhre and LAPS patients to define the clinical spectrum of SMAD4 mutations. We included 17 females and 15 males ranging in age from 8 to 48 years. Thirty were diagnosed with Myhre syndrome and two with LAPS. SMAD4 coding sequence was analyzed by Sanger sequencing. Clinical and radiological features were collected from a questionnaire completed by the referring physicians. All patients displayed a typical facial gestalt, thickened skin, joint limitation and muscular pseudohypertrophy. Growth retardation was common (68.7%) and was variable in severity (from -5.5 to -2 SD), as was mild-to-moderate intellectual deficiency (87.5%) with additional behavioral problems in 56.2% of the patients. Significant health concerns like obesity, arterial hypertension, bronchopulmonary insufficiency, laryngotracheal stenosis, pericarditis and early death occurred in four. Twenty-nine patients had a de novo heterozygous SMAD4 mutation, including both patients with LAPS. In 27 cases mutation affected Ile500 and in two cases Arg496. The three patients without SMAD4 mutations had typical findings of Myhre syndrome. Myhre-LAPS syndrome is a clinically homogenous condition with life threatening complications in the course of the disease. Our identification of SMAD4 mutations in 29/32 cases confirms that SMAD4 is the major gene responsible for Myhre syndrome.

Not all floating-harbor syndrome cases are due to mutations in exon 34 of SRCAP.

Floating-Harbor syndrome (FHS) is a rare disorder characterized by short stature, delayed bone age, speech delay, and dysmorphic facial features. We report here the molecular analysis of nine cases, fulfilling the diagnostic criteria for FHS. Using exome sequencing, we identified SRCAP as the disease gene in two cases and subsequently found SRCAP truncating mutations in 6/9 cases. All mutations occurred de novo and were located in exon 34, in accordance with the recent report of Hood et al. However, the absence of SRCAP mutations in 3/9 cases supported genetic heterogeneity of FH syndrome. Importantly, no major clinical differences were observed supporting clinical homogeneity in this series of FHS patients.

Mutations at a single codon in Mad homology 2 domain of SMAD4 cause Myhre syndrome.

Myhre syndrome (MIM 139210) is a developmental disorder characterized by short stature, short hands and feet, facial dysmorphism, muscular hypertrophy, deafness and cognitive delay. Using exome sequencing of individuals with Myhre syndrome, we identified SMAD4 as a candidate gene that contributes to this syndrome on the basis of its pivotal role in the bone morphogenetic pathway (BMP) and transforming growth factor (TGF)-ß signaling. We identified three distinct heterozygous missense SMAD4 mutations affecting the codon for Ile500 in 11 individuals with Myhre syndrome. All three mutations are located in the region of SMAD4 encoding the Mad homology 2 (MH2) domain near the site of monoubiquitination at Lys519, and we found a defect in SMAD4 ubiquitination in fibroblasts from affected individuals. We also observed decreased expression of downstream TGF-ß target genes, supporting the idea of impaired TGF-ß-mediated transcriptional control in individuals with Myhre syndrome.

Mutations in the TGFß binding-protein-like domain 5 of FBN1 are responsible for acromicric and geleophysic dysplasias.

Geleophysic (GD) and acromicric dysplasia (AD) belong to the acromelic dysplasia group and are both characterized by severe short stature, short extremities, and stiff joints. Although AD has an unknown molecular basis, we have previously identified ADAMTSL2 mutations in a subset of GD patients. After exome sequencing in GD and AD cases, we selected fibrillin 1 (FBN1) as a candidate gene, even though mutations in this gene have been described in Marfan syndrome, which is characterized by tall stature and arachnodactyly. We identified 16 heterozygous FBN1 mutations that are all located in exons 41 and 42 and encode TGFß-binding protein-like domain 5 (TB5) of FBN1 in 29 GD and AD cases. Microfibrillar network disorganization and enhanced TGFß signaling were consistent features in GD and AD fibroblasts. Importantly, a direct interaction between ADAMTSL2 and FBN1 was demonstrated, suggesting a disruption of this interaction as the underlying mechanism of GD and AD phenotypes. Although enhanced TGFß signaling caused by FBN1 mutations can trigger either Marfan syndrome or GD and AD, our findings support the fact that TB5 mutations in FBN1 are responsible for short stature phenotypes.

Molecular screening of ADAMTSL2 gene in 33 patients reveals the genetic heterogeneity of geleophysic dysplasia.

BACKGROUND: Geleophysic dysplasia (GD, OMIM 231050) is an autosomal recessive disorder characterised by short stature, small hands and feet, stiff joints, and thick skin. Patients often present with a progressive cardiac valvular disease which can lead to an early death. In a previous study including six GD families, we have mapped the disease gene on chromosome 9q34.2 and identified mutations in the A Disintegrin And Metalloproteinase with Thrombospondin repeats-like 2 gene (ADAMTSL2). METHODS: Following this study, we have collected the samples of 30 additional GD families, including 33 patients and identified ADAMTSL2 mutations in 14/33 patients, comprising 13 novel mutations. The absence of mutation in 19 patients prompted us to compare the two groups of GD patients, namely group 1, patients with ADAMTSL2 mutations (n=20, also including the 6 patients from our previous study), and group 2, patients without ADAMTSL2 mutations (n=19). RESULTS: The main discriminating features were facial dysmorphism and tip-toe walking, which were almost constantly observed in group 1. No differences were found concerning heart involvement, skin thickness, recurrent respiratory and ear infections, bronchopulmonary insufficiency, laryngo-tracheal stenosis, deafness, and radiographic features. CONCLUSIONS: It is concluded that GD is a genetically heterogeneous condition. Ongoing studies will hopefully lead to the identification of another disease gene.

Characterisation of the potential SNARE proteins relevant to milk product release by mouse mammary epithelial cells.

Casein micelles and fat globules are essential components of milk and are both secreted at the apical side of mammary epithelial cells during lactation. Milk fat globules are excreted by budding, being enwrapped by the apical plasma membrane, while caseins contained in transport vesicles are released by exocytosis. Nevertheless, the molecular mechanisms governing casein exocytosis are, to date, not fully deciphered. SNARE proteins are known to take part in cellular membrane trafficking and in exocytosis events in many cell types and we therefore attempted to identify those relevant to casein secretion. With this aim, we performed a detailed analysis of their expression by RT-PCR in both whole mouse mammary gland and in purified mammary acini at various physiological stages, as well as in the HC11 cell line. The expression of some regulatory proteins involved in SNARE complex formation such as Munc-13, Munc-18 and complexins was also explored. The amount of certain SNAREs appeared to be regulated depending on the physiological stage of the mammary gland. Co-immunoprecipitation experiments indicated that SNAP-23 interacted with syntaxin-6, -7 and -12, as well as with VAMP-3, -4 and -8 in mammary epithelial cells during lactation. Finally, the subcellular localisation of candidate SNAREs in these cells was determined both by indirect immunofluorescence and immunogold labelling. The present work provides important new data concerning SNARE proteins in mammary epithelial cells and points to SNAP-23 as a potential central player for the coupling of casein and milk fat globule secretion during lactation.