Ozge Ozalp Yuregir

Molecular etiology of arthrogryposis in multiple families of mostly Turkish origin

BACKGROUND Arthrogryposis, defined as congenital joint contractures in 2 or more body areas, is a clinical sign rather than a specific disease diagnosis. To date, more than 400 different disorders have been described that present with arthrogryposis, and variants of more than 220 genes have been associated with these disorders; however, the underlying molecular etiology remains unknown in the considerable majority of these cases. METHODS We performed whole exome sequencing (WES) of 52 patients with clinical presentation of arthrogryposis from 48 different families. RESULTS Affected individuals from 17 families (35.4%) had variants in known arthrogryposis-associated genes, including homozygous variants of cholinergic γ nicotinic receptor (CHRNG, 6 subjects) and endothelin converting enzyme-like 1 (ECEL1, 4 subjects). Deleterious variants in candidate arthrogryposis-causing genes (fibrillin 3 [FBN3], myosin IXA [MYO9A], and pleckstrin and Sec7 domain containing 3 [PSD3]) were identified in 3 families (6.2%). Moreover, in 8 families with a homozygous mutation in an arthrogryposis-associated gene, we identified a second locus with either a homozygous or compound heterozygous variant in a candidate gene (myosin binding protein C, fast type [MYBPC2] and vacuolar protein sorting 8 [VPS8], 2 families, 4.2%) or in another disease-associated genes (6 families, 12.5%), indicating a potential mutational burden contributing to disease expression. CONCLUSION In 58.3% of families, the arthrogryposis manifestation could be explained by a molecular diagnosis; however, the molecular etiology in subjects from 20 families remained unsolved by WES. Only 5 of these 20 unrelated subjects had a clinical presentation consistent with amyoplasia; a phenotype not thought to be of genetic origin. Our results indicate that increased use of genome-wide technologies will provide opportunities to better understand genetic models for diseases and molecular mechanisms of genetically heterogeneous disorders, such as arthrogryposis. FUNDING This work was supported in part by US National Human Genome Research Institute (NHGRI)/National Heart, Lung, and Blood Institute (NHLBI) grant U54HG006542 to the Baylor-Hopkins Center for Mendelian Genomics, and US National Institute of Neurological Disorders and Stroke (NINDS) grant R01NS058529 to J.R. Lupski.

Mutations in CDC45, Encoding an Essential Component of the Pre-initiation Complex, Cause Meier-Gorlin Syndrome and Craniosynostosis

DNA replication precisely duplicates the genome to ensure stable inheritance of genetic information. Impaired licensing of origins of replication during the G1 phase of the cell cycle has been implicated in Meier-Gorlin syndrome (MGS), a disorder defined by the triad of short stature, microtia, and a/hypoplastic patellae. Biallelic partial loss-of-function mutations in multiple components of the pre-replication complex (preRC; ORC1, ORC4, ORC6, CDT1, or CDC6) as well as de novo stabilizing mutations in the licensing inhibitor, GMNN, cause MGS. Here we report the identification of mutations in CDC45 in 15 affected individuals from 12 families with MGS and/or craniosynostosis. CDC45 encodes a component of both the pre-initiation (preIC) and CMG helicase complexes, required for initiation of DNA replication origin firing and ongoing DNA synthesis during S-phase itself, respectively, and hence is functionally distinct from previously identified MGS-associated genes. The phenotypes of affected individuals range from syndromic coronal craniosynostosis to severe growth restriction, fulfilling diagnostic criteria for Meier-Gorlin syndrome. All mutations identified were biallelic and included synonymous mutations altering splicing of physiological CDC45 transcripts, as well as amino acid substitutions expected to result in partial loss of function. Functionally, mutations reduce levels of full-length transcripts and protein in subject cells, consistent with partial loss of CDC45 function and a predicted limited rate of DNA replication and cell proliferation. Our findings therefore implicate the preIC as an additional protein complex involved in the etiology of MGS and connect the core cellular machinery of genome replication with growth, chondrogenesis, and cranial suture homeostasis.

Rare Variants in the Notch Signaling Pathway Describe a Novel Type of Autosomal Recessive Klippel-Feil Syndrome

Klippel–Feil syndrome is a rare disorder represented by a subgroup of segmentation defects of the vertebrae and characterized by fusion of the cervical vertebrae, low posterior hairline, and short neck with limited motion. Both autosomal dominant and recessive inheritance patterns were reported in families with Klippel–Feil. Mutated genes for both dominant (GDF6 and GDF3) and recessive (MEOX1) forms of Klippel–Feil syndrome have been shown to be involved in somite development via transcription regulation and signaling pathways. Heterotaxy arises from defects in proteins that function in the development of left–right asymmetry of the developing embryo. We describe a consanguineous family with a male proband who presents with classical Klippel–Feil syndrome together with heterotaxy (situs inversus totalis). The present patient also had Sprengels deformity, deformity of the sternum, and a solitary kidney. Using exome sequencing, we identified a homozygous frameshift mutation (c.299delT; p.L100fs) in RIPPLY2, a gene shown to play a crucial role in somitogenesis and participate in the Notch signaling pathway via negatively regulating Tbx6. Our data confirm RIPPLY2 as a novel gene for autosomal recessive Klippel–Feil syndrome, and in addition—from a mechanistic standpoint—suggest the possibility that mutations in RIPPLY2 could also lead to heterotaxy.

NONSENSE β-THALASSEMIA MUTATION AT CODON 37 (TGG>TGA), DETECTED FOR THE FIRST TIME IN THREE TURKISH CASES

Thalassemias are genetically heterogeneous group of disorders with reduced or absent production of globin. β-Thalassemia major can be caused by homozygosity or compound heterozygosity for β-globin gene mutation. Here we report, for the first time in Turkey, three cases who carry the nonsense β-thalassemia (β-thal) mutation at codon 37 (TGG>TGA; Trp→Stop) causing premature stop codon.

Phenotypic expansion illuminates multilocus pathogenic variation

PurposeMultilocus variation—pathogenic variants in two or more disease genes—can potentially explain the underlying genetic basis for apparent phenotypic expansion in cases for which the observed clinical features extend beyond those reported in association with a “known” disease gene.MethodsAnalyses focused on 106 patients, 19 for whom apparent phenotypic expansion was previously attributed to variation at known disease genes. We performed a retrospective computational reanalysis of whole-exome sequencing data using stringent Variant Call File filtering criteria to determine whether molecular diagnoses involving additional disease loci might explain the observed expanded phenotypes.ResultsMultilocus variation was identified in 31.6% (6/19) of families with phenotypic expansion and 2.3% (2/87) without phenotypic expansion. Intrafamilial clinical variability within two families was explained by multilocus variation identified in the more severely affected sibling.ConclusionOur findings underscore the role of multiple rare variants at different loci in the etiology of genetically and clinically heterogeneous cohorts. Intrafamilial phenotypic and genotypic variability allowed a dissection of genotype–phenotype relationships in two families. Our data emphasize the critical role of the clinician in diagnostic genomic analyses and demonstrate that apparent phenotypic expansion may represent blended phenotypes resulting from pathogenic variation at more than one locus.

The Prevalence of Gap Junction Protein Beta 2 (GJB2) Mutations in Non Syndromic Sensorineural Hearing Loss in Cukurova Region.

OBJECTIVE To date, studies in all populations showed that mutations in the gene of Gap junction protein beta 2 (GJB2) play an important role in non-syndromic autosomal recessive congenital hearing loss. The aim of this study was to evaluate GJB2 gene of patients with hearing loss in our region using deoxyribonucleic acid (DNA) sequencing method and to demonstrate region-specific mutation and polymorphism distribution. MATERIALS AND METHODS Patients who had bilateral severe sensorineural non-syndromic hearing loss identified by audiologic evaluation were included. Peripheral blood samples were collected and the GJB2 gene exon1 and exon 2 regions were amplified by polymerase chain reaction (PCR). Obtained PCR products were sequenced by the DNA sequence analysis method (SeqFinder Sequencing System; ABI 3130; Foster City, CA, USA) and analyzed using the SeqScape software. RESULTS Of the 77 patients, 16 had homozygous or heterozygous mutation. CONCLUSION The mutation of 35delG, which is known as the most frequent mutation of GJB2 gene, was also the most frequently seen mutation at a ratio of 5.5% in patients with hearing loss in our region; this was followed by the V27I mutation. As this is the first study conducted by sequence analysis in our region, it was worth to be presented in terms of showing the distribution of mutation.

Hypomyelination and congenital cataract: Identification of novel mutations in two unrelated families

BACKGROUND Hypomyelination and congenital cataract (HCC) is a rare autosomal recessive white matter disorder characterized by congenital cataract, progressive neurologic impairment, and myelin deficiency in the central and peripheral nervous system, caused by mutations in the FAM126A gene. AIMS To report three patients of two unrelated families segregating novel mutations. METHODS clinical, neurophysiological, neuroradiologic and molecular investigations were carried out. RESULTS All patients show bilateral congenital cataract and progressive neurological impairment with peripheral neuropathy. The clinical phenotype is consistent with the severe form of HCC. Brain magnetic resonance imaging show the combination of a diffuse hypomyelination with superimposed periventricular white matter signal abnormalities. CONCLUSIONS this study describes three additional HCC patients indicating that this recently defined leukoencephalopathy should be included in the differential diagnosis of hypomyelination in childhood. The peculiar clinical and neuroradiologic findings are useful to properly address molecular investigations and allow the differential diagnosis between HCC and other hypomyelinating forms.

Plasminogen activator inhibitor-1 5G/5G genotype is associated with early spontaneous recanalization of the infarct-related artery in patients presenting with acute ST-elevation myocardial infarction.

BackgroundWe aimed to examine the association between plasminogen activator inhibitor-1 (PAI-1) genetic polymorphism and early spontaneous recanalization in patients presenting with acute ST-elevation myocardial infarction. MethodsPatients admitted to our emergency department with ST-elevation myocardial infarction in the first 6 h of symptom onset were included. An immediate primary percutaneous coronary intervention was performed. Patients were grouped according to the initial patency of the infarct-related artery (IRA) as follows: total occlusion (TO) group [Thrombolysis in Myocardial Infarction (TIMI) 0–1 flow in the IRA], partial recanalization group (TIMI 2 flow in the IRA), and complete recanalization (CR) group (TIMI 3 flow in the IRA). PAI-1 4G/5G polymorphism was detected using the real-time PCR method. ResultsThere were 107 patients in the TO group, 30 patients in the partial recanalization group, and 45 patients in the CR group. When we evaluated degrees of patency according to the PAI-1 genotype, TO of the IRA was the highest in patients with the PAI 4G/4G genotype (PAI-1 4G/4G: 66.7%, PAI-1 4G/5G: 65.9%, PAI-1 5G/5G: 40.4%) and CR of the IRA was the highest in patients with the PAI 5G/5G genotype (PAI-1 5G/5G: 38.5%, PAI-1 4G/5G: 19.8%, PAI-1 4G/4G: 17.9%). The distribution of genotypes in different degrees of patency of IRA was statistically significant (P=0.029). In logistic regression analysis, the PAI-1 5G/5G genotype was associated independently with the spontaneous CR of the IRA (odds ratio: 2.875, 95% confidence interval [1.059–7.086], P=0.038). ConclusionPatients with the PAI-1 5G/5G genotype seem to be luckier than others in terms of early spontaneous recanalization of the IRA. Further prospective studies with large patient populations are required for more precise results.

The TWIST2 mutation causes Setleis syndrome: a rare clinical case report.

The focal facial dermal dysplasias are a group of inherited, rare disorders of facial development characterized by bitemporal or preauricular scar-like defects resembling ‘forceps marks’. Four subtypes have been delineated, and the mutations in the TWIST2 gene have been identified in type-III focal facial dermal dysplasia, Setleis Syndrome (SS). We describe a boy with the hallmark bitemporal scarlike lesions (like forceps marks) and other characteristic clinical features of SS. Of those, coarse facial appearance with sparse lateral eyebrow and eyelashes, high-arched eyebrows, periorbital puffiness, downslanting palpebral fissure and poor vocalization were the main findings. Molecular genetic analysis of TWIST2 revealed a homozygous p.Leu109Pro (c.326T>C) mutation in the first exon of the gene. Heterozygous p.Leu109Pro mutation was also identified in his parents and his brother with milder dysmorphic facial features including prominent chin, long face, sparse eyebrows and eyelashes and other features like inguinal and umblical hernia. Molecular analysis of family members and a consanguineous marriage supported the autosomal recessive inheritance of SS in this family. This study indicated that heterozygous individuals carrying TWIST2 p.Leu109Pro mutation may also display some clinical features of SS at milder levels. Clin Dysmorphol 26:128–131 Copyright

Shprintzen-Goldberg Syndrome: Case Report

Shprintzen-Goldberg syndrome (SGS), is a syndrome characterized by typical dysmorphic features, craniosynostosis and marfanoid Shprintzen-Goldberg syndrome is a rare syndrome with craniosynostosis of coronal, sagittal or lambdoidal sutures, dolichocephaly, typical craniofacial features, skeletal abnormalities, scoliosis, joint hyperextensibility or contractures, neurological findings and brain malformations. Fifteen months old male patient with hydrocephalus and dysmorphic facial appearance was referred to our clinic for genetical evaluation. In his dysmorphic examination, the findings were dolichocephaly, prominent forehead and glabella, hypertelorism, prominent eyes, proptosis, depressed nasal root, anteverted nostrils, small nose, low-set and posteriorly rotated, dysplastic ears, microretrognathia, short philtrum, fish mouth of mouth, plump cheeks, high and narrow palate, secondary alveolar arch, pectus carinatum. Hands were small and he had arachnodactyly. Toes were thin. He had also hypotonia and umbilical hernia. With these findings, he was clinically diagnosed as Shprintzen-Goldberg syndrome. This is the first reported case of ShprintzenGoldberg syndrome from Turkey according to literature review.