Asuman Koparir

Novel MASP1 mutations are associated with an expanded phenotype in 3MC1 syndrome

Background3MC1 syndrome is a rare autosomal recessive disorder characterized by intellectual disability, short stature and distinct craniofacial, umbilical, and sacral anomalies. Five mutations in MASP1, encoding lectin complement pathway enzymes MASP-1 and MASP-3, have thus far been reported to cause 3MC1 syndrome. Only one previously reported mutation affects both MASP-1 and MASP-3, while the other mutations affect only MASP-3.MethodsWe evaluated six unrelated individuals with 3MC1 syndrome and performed Sanger sequencing for all coding exons of MASP1. We also measured complement lectin and alternative pathway activities in an affected individual’s serum.ResultsWe found two novel splice site mutations, c.1012-2A > G in one and c.891 + 1G > T in two probands, and three novel missense mutations, c.1451G > A (p.G484E), c.1657G > A (p.D553N), and c.1987G > T (p.D663Y). Missense mutations affect only MASP-3, while splice site mutations affect both MASP-1 and MASP-3. In a proband who is homozygous for c.891 + 1G > T, we detected a total lack of lectin complement pathway activity and a 2.5-fold lower alternative pathway activity. The phenotype observed in patients whose both MASP-1 and MASP-3 are affected and in those whose only MASP-3 is affected does not appear to be different. We observed structural brain abnormalities, neonatal tooth, a vascular anomaly and a solid lesion in liver as novel phenotypic features of 3MC1 syndrome.ConclusionNovel mutations and additional phenotypic features expand the genotypic and phenotypic spectrum of 3MC1 syndrome. Although patients with MASP-1 dysfunction in addition to disrupted MASP-3 have an altered complement system, their disease phenotype is not different from those having only MASP-3 dysfunction.

Novel POC1A mutation in primordial dwarfism reveals new insights for centriole biogenesis

POC1A encodes a WD repeat protein localizing to centrioles and spindle poles and is associated with short stature, onychodysplasia, facial dysmorphism and hypotrichosis (SOFT) syndrome. These main features are related to the defect in cell proliferation of chondrocytes in growth plate. In the current study, we aimed at identifying the molecular basis of two patients with primordial dwarfism (PD) in a single family through utilization of whole-exome sequencing. A novel homozygous p.T120A missense mutation was detected in POC1A in both patients, a known causative gene of SOFT syndrome, and confirmed using Sanger sequencing. To test the pathogenicity of the detected mutation, primary fibroblast cultures obtained from the patients and a control individual were used. For evaluating the global gene expression profile of cells carrying p.T120A mutation in POC1A, we performed the gene expression array and compared their expression profiles to those of control fibroblast cells. The gene expression array analysis showed that 4800 transcript probes were significantly deregulated in cells with p.T120A mutation in comparison to the control. GO term association results showed that deregulated genes are mostly involved in the extracellular matrix and cytoskeleton. Furthermore, the p.T120A missense mutation in POC1A caused the formation of abnormal mitotic spindle structure, including supernumerary centrosomes, and changes in POC1A were accompanied by alterations in another centrosome-associated WD repeat protein p80-katanin. As a result, we identified a novel mutation in POC1A of patients with PD and showed that this mutation causes the formation of multiple numbers of centrioles and multipolar spindles with abnormal chromosome arrangement.

Poikiloderma with neutropenia: genotype-ethnic origin correlation, expanding phenotype and literature review.

Poikiloderma with neutropenia (PN), is a rare genodermatosis associated with patognomic features of poikiloderma and permanent neutropenia. Three common recurrent mutations of related gene, USB1, were considered to be associated with three different ethnic origins. The most common recurrent mutation, c.531delA, has been detected in seven Caucasian patients in the literature. In this paper, we present review of all patients from the literature and report two additional patients of Turkish ancestry with the diagnosis of PN. The diagnosis of these two PN patients were made clinically and confirmed by molecular analysis which detected the most common recurrent mutation, c.531delA. Genotype‐ethnic origin correlation hypothesis, therefore, has been strengthened with this result. Short stature in PN, is a common finding, which until now has never been treated with growth hormone (GH). One of our patients is the first patient with attempted treatment of short stature via GH administration. Finally, both of our patients had high‐pitched voice and vocal cord nodules which might be considered as additional clinical findings not associated with PN before.

Circumferential skin folds and multiple anomalies: confirmation of a distinct autosomal recessive Michelin tire baby syndrome

Department of Medical Genetics, Cerrahpasa Medical School of Istanbul University, Department of Pediatrics, Medical School of Bezmi Alem University, Istanbul and Department of Medical Genetics, Medical School of Osmangazi University, Eskisehir, Turkey Correspondence to Hakan Ulucan MD, PhD, Department of Medical Genetics, Cerrahpasa Medical School of Istanbul University, Istanbul 34098, Turkey Tel: + 90 212 414 30 00 x22 996; fax: + 90 212 414 31 84; e-mail: hulucan@istanbul.edu.tr

Whole-exome sequencing revealed two novel mutations in Usher syndrome.

Usher syndrome is a clinically and genetically heterogeneous autosomal recessive inherited disorder accompanied by hearing loss and retinitis pigmentosa (RP). Since the associated genes are various and quite large, we utilized whole-exome sequencing (WES) as a diagnostic tool to identify the molecular basis of Usher syndrome. DNA from a 12-year-old male diagnosed with Usher syndrome was analyzed by WES. Mutations detected were confirmed by Sanger sequencing. The pathogenicity of these mutations was determined by in silico analysis. A maternally inherited deleterious frameshift mutation, c.14439_14454del in exon 66 and a paternally inherited non-sense c.10830G>A stop-gain SNV in exon 55 of USH2A were found as two novel compound heterozygous mutations. Both of these mutations disrupt the C terminal of USH2A protein. As a result, WES revealed two novel compound heterozygous mutations in a Turkish USH2A patient. This approach gave us an opportunity to have an appropriate diagnosis and provide genetic counseling to the family within a reasonable time.

Revealing the function of a novel splice-site mutation of CHD7 in CHARGE syndrome.

Most cases of CHARGE syndrome are sporadic and autosomal dominant. CHD7 is a major causative gene of CHARGE syndrome. In this study, we screened CHD7 in two Turkish patients demonstrating symptoms of CHARGE syndrome such as coloboma, heart defect, choanal atresia, retarded growth, genital abnomalities and ear anomalies. Two mutations of CHD7 were identified including a novel splice-site mutation (c.2443-2A>G) and a previously known frameshift mutation (c.2504_2508delATCTT). We performed exon trapping analysis to determine the effect of the c.2443-2A>G mutation at the transcriptional level, and found that it caused a complete skip of exon 7 and splicing at a cryptic splice acceptor site. Our current study is the second study demonstrating an exon 7 deficit in CHD7. Results of previous studies suggest that the c.2443-2A>G mutation affects the formation of nasal tissues and the neural retina during early development, resulting in choanal atresia and coloboma, respectively. The findings of the present study will improve our understanding of the genetic causes of CHARGE syndrome.

Renal involvement in patients with mucolipidosis IIIalpha/beta: Causal relation or co-occurrence?

Mucolipidosis IIIalpha/beta (MLIIIalpha/beta) is a rare lysosomal storage disorder characterized by childhood onset of flexion contractures of fingers, joint stiffness in the shoulders, hips, and knees, and mild short stature. Recessive mutations in the GNPTAB gene have been associated with MLIIIalpha/beta. We present five children aged 9–16 years from a large kindred family whose serum activities of several lysosomal enzymes were significantly elevated. Whole exome sequencing followed by confirmation by Sanger sequencing identified a novel homozygous missense mutation (c.22 A > G; p.R8G) in the GNPTAB gene in all affected subjects. The five patients initially presented with flexion contractures of fingers followed by stiffnes of large joints. Only two affected boys also had a nephrotic‐range proteinuria. Renal biopsy showed focal segmental glomerulosclerosis and foamy appearance of glomerular visceral epithelial cells which were compatible with storage disease. No other known causes of proteinuria could be detected by both laboratory and biopsy findings. There was no known family history of hereditary kidney disease, and healthy siblings and parents had normal renal function and urinalysis. These findings suggest that the renal involvement probably due to MLIIIalpha/beta, although it can still be present by coincidence in the two affected patients.

A novel frameshift mutation and infrequent clinical findings in two cases with Dyggve-Melchior-Clausen syndrome.

Dyggve–Melchior–Clausen syndrome (DMC) (MIM #223800) is a rare autosomal-recessive type of skeletal dysplasia accompanied by variable degrees of intellectual disability (ID). It is characterized by progressive spondyloepimetaphyseal dysplasia leading to disproportionate short stature, microcephaly, and coarse facies. The radiographic appearance of generalized platyspondyly with double-humped end plates and the lace-like appearance of iliac crests are pathognomonic in this syndrome. The disorder results from mutations in the dymeclin (DYM) mapped to the 18q12–12.1 chromosomal region. Here, we report two cases with DMC: one with disproportionate short stature, developmental delay, and severe ID with a novel frameshift mutation (c.1028_1056del29) leading to a premature stop codon, and the second patient with classical clinical and radiological features of DMC with mild ID and rectal prolapse, which is very rare. The clinical diagnosis was confirmed with molecular analysis of DYM with a known mutation at c.580C>T (p.R194X). The parents and sibling of the second patient were heterozygous carriers with mild skeletal changes and short stature.