Choline acetyltransferase (ChAT; EC 2.3.1.6) catalyzes synthesis of acetylcholine from acetyl-CoA and choline in cholinergic neurons. Mutations in CHAT (MIM # 118490) cause potentially lethal congenital myasthenic syndromes associated with episodic apnea (ChAT-CMS) (MIM # 254210). Here we analyze the functional consequences of 12 missense and 1 nonsense mutations of CHAT in 11 patients. Nine of the mutations are novel. We examine expression of the recombinant missense mutants in Bosc 23 cells, determine their kinetic properties and thermal stability, and interpret the functional effects of 11 mutations in the context of the atomic structural model of human ChAT. Five mutations (p.Trp421Ser, p.Ser498Pro, p.Thr553Asn, p.Ala557Thr, p.Ser572Trp) reduce enzyme expression to <50% of wild-type. Mutations with severe kinetic effects are located in the active-site tunnel (p.Met202Arg, p.Thr553Asn and p.Ala557Thr) or adjacent to the substrate binding site (p.Ser572Trp), or exert their effect allosterically (p.Trp421Ser and p.Ile689Ser). Two mutations with milder kinetic effects (p.Val136Met, p.Ala235Thr) are also predicted to act allosterically. One mutation (p.Thr608Asn) below the nucleotide binding site of CoA enhances dissociation of AcCoA from the enzyme-substrate complex. Two mutations introducing a proline residue into an α-helix (p.Ser498Pro and p.Ser704Pro) impair the thermal stability of ChAT.

Genetics is the study of heredity, which means the study of genes and factors related to all aspects of genes. The scientific history of genetics began with the works of Gregor Mendel in the mid-19th century. Prior to Mendel, genetics was primarily theoretical whilst, after Mendel, the science of genetics was broadened to include experimental genetics. Developments in all fields of genetics and genetic technology in the first half of the 20th century provided a basis for the later developments. In the second half of the 20th century, the molecular background of genetics has become more understandable. Rapid technological advancements, followed by the completion of Human Genome Project, have contributed a great deal to the knowledge of genetic factors and their impact on human life and diseases. Currently, more than 1800 disease genes have been identified, more than 2000 genetic tests have become available, and in conjunction with this at least 350 biotechnology-based products have been released onto the market. Novel technologies, particularly next generation sequencing, have dramatically accelerated the pace of biological research, while at the same time increasing expectations. In this paper, a brief summary of genetic history with short explanations of most popular genetic techniques is given.

Otofaciocervical syndrome (OFCS) is an autosomal recessively inherited disorder characterized by facial dysmorphism, external ear anomalies with preauricular pits and hearing impairment, branchial cysts or fistulas, anomalies of the vertebrae and the shoulder girdle, and mild intellectual disability. In a large consanguineous family with OFCS from Turkey, we performed whole-exome sequencing (WES) of a single pooled DNA sample of four affected individuals. Filtering for variants with a percentage of alternate reads ≥ 90 % and a coverage of at least five reads identified only a single novel homozygous variant, c.497G>T, located in PAX1 that co-segregated with the disease in the family. PAX1 encodes a transcription factor with a critical role in pattern formation during embryogenesis in vertebrates. The mutation is predicted to substitute the glycine at position 166 to valine (p.G166V) within the highly conserved paired-box domain of the PAX1 protein. We performed a dual luciferase reporter assay to examine the transactivation of a regulatory sequence in the Nkx3-2 promoter region, which is a direct target of mouse Pax1 transcriptional regulation. We observed a significantly reduced transactivation in HEK293T cells overexpressing Pax1(G157V) in comparison to Pax1(WT) expressing cells, indicating a reduced DNA-binding affinity of the mutant protein. Taken together, our results show that the strategy of pooling DNA is a powerful, cost-effective application for WES in consanguineous families and establish PAX1 as a new disease-causing gene for OFCS and as part of the EYA-DACH-SIX-PAX network, important in early embryogenesis.

Alström Syndrome is an autosomal recessive disease characterized by multiple organ involvement, including neurosensory vision and hearing loss, childhood obesity, diabetes mellitus, cardiomyopathy, hypogonadism, and pulmonary, hepatic, renal failure, and systemic fibrosis. Alström Syndrome is caused by mutations in ALMS1, and ALMS1 protein is thought to play a role in microtubule organization, intraflagellar transport, endosome recycling and cell cycle regulation. Here, we report extensive phenotypic and genetic analysis of a large cohort of Turkish patients with Alström Syndrome. We evaluated 61 Turkish patients, including 11 previously reported, for both clinical spectrum and mutations in ALMS1. To reveal the molecular diagnosis of the patients, there different approaches were used in combination, a cohort of patients were screened by the gene array to detect the common mutations in ALMS1 gene, then in patients having any of common ALMS1 mutations were subjected to direct DNA sequencing or next generation sequencing for the screening of mutations in all coding regions of the gene. In total, 20 distinct disease-causing nucleotide changes in ALMS1 have been identified, 8 of which are novel, thereby increasing the reported ALMS1 mutations by 6% (8/120). Five disease-causing variants were identified in more than one kindred, but most alleles were unique to each single patient and identified only once (16/20). So far, 16 mutations identified were specific to the Turkish population, and four have also been reported in other ethnicities. Additionally, 49 variants of uncertain pathogenicity were noted, and four of these were very rare and probably or likely deleterious according to in silico mutation prediction analyses. Alström Syndrome has a relatively high incidence in Turkey and the present study shows that the ALMS1 mutations are largely heterogeneous; thus, these data from a particular population may provide a unique source for the identification of additional mutations underlying Alström Syndrome and contribute to genotype-phenotype correlation studies.

Objective: The objective of this study was to evaluate the incidence and reasons for referrals for prenatally detected Turner syndrome and cystic hygroma cases among prenatal cases performed between 1998 and 2007. Methods: In this study 3,595 amniocentesis, chorionic villus and cordocenthesis materials obtained between 1998 and 2007 were evaluated. Among prenatal cases, 23 Turner syndrome cases were also evaluated according to their referral reasons. Among the indications of prenatal cases, cystic hygroma was evaluated according to karyotype results. Results: Twenty-three cases were Turner Syndrome in which 7 cases were detected to have mosaic pattern. The indications for prenatal diagnosis for the cases were cystic hygroma in 11 cases, missed abortion in 6 cases, advanced maternal age in 5 cases and positive screening test results in 1 case. Among 18 cases having cystic hygroma detected by ultrasonography, 8 cases (44.4%) were found to have a 45,X karyotype, 3 cases were found to be mosaic Turner syndrome (16.7%), 5 cases (27.7%) had normal karyotype, 1 case (5.6%) 47,XX,+13 and 1 case (5.6%) 47,XX,+21. Conclusion: The present study indicates the importance of cystic hygroma in prenatal diagnosis of Turner Syndrome and other aneuploidies.