Identification and Characterization of Novel Founder Mutations in : Refining the Genetic Landscape of Charcot-Marie-Tooth Disease Type 4D in Bulgaria.

Charcot-Marie-Tooth neuropathy type 4D (CMT4D) is a rare genetic disorder of the peripheral nervous system caused by biallelic mutations in the N-Myc Downstream Regulated 1 gene (). Patients present with an early onset demyelinating peripheral neuropathy causing severe distal muscle weakness and sensory loss, leading to loss of ambulation and progressive sensorineural hearing loss. The disorder was initially described in the Roma community due to a common founder mutation, and only a handful of disease-causing variants have been described in this gene so far.

WGS Revealed Novel Pathogenic Variants, Missed by WES, Causing Ciliary Structure and Function Defects.

Bardet-Biedl syndrome (BBS) is an autosomal recessive ciliopathy that affects multiple organs, leading to retinitis pigmentosa, polydactyly, obesity, renal anomalies, cognitive impairment, and hypogonadism. Until now, biallelic pathogenic variants have been identified in at least 24 genes delineating the genetic heterogeneity of BBS. Among those, is a minor contributor to the mutation load and is one of the eight subunits forming the BBSome, a protein complex implied in protein trafficking within the cilia.

MLPA followed by target-NGS to detect mutations in the dystrophin gene of Peruvian patients suspected of DMD/DMB.

Background: We report the molecular analysis of the DMD gene in a group of Peruvian patients with Duchenne/Becker dystrophinopathy. This is the first study to thoroughly characterize mutations in this population.

Methods: We used the combination of multiplex ligation-dependent probe amplification (MLPA) and sequencing analysis of the DMD gene.

[Detection of mutations causing Duchenne and Becker muscular dystrophies: multiplex polymerase chain reaction vs. Multiplex ligation dependent probe amplification].

Duchenne and Becker muscular dystrophies are rare diseases that receive limited attention in our field. The objective of this study was to implement the Multiplex Ligation-dependent Probe Amplification technique (MLPA) and to demonstrate that it has advantages over the Multiplex Polymerase Chain Reaction (Multiplex PCR) technique. Samples from 40 individuals with a presumptive diagnosis of Duchenne and Becker muscular dystrophies were analyzed: first by Multiplex PCR and then by MLPA.

Novel IQCE variations confirm its role in postaxial polydactyly and cause ciliary defect phenotype in zebrafish.

Polydactyly is one of the most frequent inherited defects of the limbs characterized by supernumerary digits and high-genetic heterogeneity. Among the many genes involved, either in isolated or syndromic forms, eight have been implicated in postaxial polydactyly (PAP). Among those, IQCE has been recently identified in a single consanguineous family.

Kufor-Rakeb Syndrome/PARK9: One Novel and One Possible Recurring Ashkenazi ATP13A2 Mutation.

Kufor-Rakeb syndrome (KRS)/PARK9 presents with autosomal recessive young onset Parkinson's disease (YOPD), spastic paraparesis, abnormal eye movements and facial myokymia. KRS is caused by homozygous/compound heterozygous inactivating mutations in ATP13A2. Two affected siblings (born to non-consanguineous Jewish parents) presenting a similar KRS phenotype (onset age 27, 23), carried compound heterozygous pathogenic variants in ATP13A2: c.

MCM3AP in recessive Charcot-Marie-Tooth neuropathy and mild intellectual disability.

Defects in mRNA export from the nucleus have been linked to various neurodegenerative disorders. We report mutations in the gene MCM3AP, encoding the germinal center associated nuclear protein (GANP), in nine affected individuals from five unrelated families. The variants were associated with severe childhood onset primarily axonal (four families) or demyelinating (one family) Charcot-Marie-Tooth neuropathy.

Loss-of-function mutations in the ATP13A2/PARK9 gene cause complicated hereditary spastic paraplegia (SPG78).

Hereditary spastic paraplegias are heterogeneous neurodegenerative disorders characterized by progressive spasticity of the lower limbs due to degeneration of the corticospinal motor neurons. In a Bulgarian family with three siblings affected by complicated hereditary spastic paraplegia, we performed whole exome sequencing and homozygosity mapping and identified a homozygous p.Thr512Ile (c.

Sphingosine 1-phosphate lyase deficiency causes Charcot-Marie-Tooth neuropathy.

Objective: To identify the unknown genetic cause in a nuclear family with an axonal form of peripheral neuropathy and atypical disease course.

Methods: Detailed neurologic, electrophysiologic, and neuropathologic examinations of the patients were performed. Whole exome sequencing of both affected individuals was done.

Novel mutations in genes causing hereditary spastic paraplegia and Charcot-Marie-Tooth neuropathy identified by an optimized protocol for homozygosity mapping based on whole-exome sequencing.

Purpose: Homozygosity mapping is an effective approach for detecting molecular defects in consanguineous families by delineating stretches of genomic DNA that are identical by descent. Constant developments in next-generation sequencing created possibilities to combine whole-exome sequencing (WES) and homozygosity mapping in a single step.

Methods: Basic optimization of homozygosity mapping parameters was performed in a group of families with autosomal-recessive (AR) mutations for which both single-nucleotide polymorphism (SNP) array and WES data were available.

Clinical characteristics of rod and cone photoreceptor dystrophies in patients with mutations in the C8orf37 gene.

Purpose: To provide the clinical features in patients with retinal disease caused by C8orf37 gene mutations.

Methods: Eight patients--four diagnosed with retinitis pigmentosa (RP) and four with cone-rod dystrophy (CRD), carrying causal C8orf37 mutations--were clinically evaluated, including extensive medical history taking, slit-lamp biomicroscopy, ophthalmoscopy, kinetic perimetry, electroretinography (ERG), spectral-domain optical coherence tomography (SD-OCT), autofluorescence (AF) imaging, and fundus photography.

Results: In families A and D, respectively, one and three patients showed a classic RP phenotype with night blindness followed by concentric loss of visual field.

Union makes strength: a worldwide collaborative genetic and clinical study to provide a comprehensive survey of RD3 mutations and delineate the associated phenotype.

Leber congenital amaurosis (LCA) is the earliest and most severe retinal degeneration (RD), and the most common cause of incurable blindness diagnosed in children. It is occasionally the presenting symptom of multisystemic ciliopathies which diagnosis will require a specific care of patients. Nineteen LCA genes are currently identified and three of them account for both non-syndromic and syndromic forms of the disease.

BBS1 mutations in a wide spectrum of phenotypes ranging from nonsyndromic retinitis pigmentosa to Bardet-Biedl syndrome.

Objective: To investigate the involvement of the Bardet-Biedl syndrome (BBS) gene BBS1 p.M390R variant in nonsyndromic autosomal recessive retinitis pigmentosa (RP).

Methods: Homozygosity mapping of a patient with isolated RP was followed by BBS1 sequence analysis.

Non-syndromic retinal ciliopathies: translating gene discovery into therapy.

Homozygosity mapping and exome sequencing have accelerated the discovery of gene mutations and modifier alleles implicated in inherited retinal degeneration in humans. To date, 158 genes have been found to be mutated in individuals with retinal dystrophies. Approximately one-third of the gene defects underlying retinal degeneration affect the structure and/or function of the 'connecting cilium' in photoreceptors.

Mutations in C8orf37, encoding a ciliary protein, are associated with autosomal-recessive retinal dystrophies with early macular involvement.

Cone-rod dystrophy (CRD) and retinitis pigmentosa (RP) are clinically and genetically overlapping heterogeneous retinal dystrophies. By using homozygosity mapping in an individual with autosomal-recessive (ar) RP from a consanguineous family, we identified three sizeable homozygous regions, together encompassing 46 Mb. Next-generation sequencing of all exons, flanking intron sequences, microRNAs, and other highly conserved genomic elements in these three regions revealed a homozygous nonsense mutation (c.

IQCB1 mutations in patients with leber congenital amaurosis.

Purpose: Leber congenital amaurosis (LCA) is genetically heterogeneous, with 15 genes identified thus far, accounting for ∼70% of LCA patients. The aim of the present study was to identify new genetic causes of LCA.

Methods: Homozygosity mapping in >150 LCA patients of worldwide origin was performed with high-density SNP microarrays to identify new disease-causing genes.

Candidate exome capture identifies mutation of SDCCAG8 as the cause of a retinal-renal ciliopathy.

Nephronophthisis-related ciliopathies (NPHP-RC) are recessive disorders that feature dysplasia or degeneration occurring preferentially in the kidney, retina and cerebellum. Here we combined homozygosity mapping with candidate gene analysis by performing 'ciliopathy candidate exome capture' followed by massively parallel sequencing. We identified 12 different truncating mutations of SDCCAG8 (serologically defined colon cancer antigen 8, also known as CCCAP) in 10 families affected by NPHP-RC.

Three novel polymorphic microsatellite markers for the glaucoma locus GLC1B by datamining tetranucleotide repeats on chromosome 2p12-q12.

In order to identify new markers around the glaucoma locus GLC1B as a tool to refine its critical region at 2p11.2-2q11.2, we searched the critical region sequence obtained from the UCSC database for tetranucleotide (GATA)n and (GTCT)n repeats of at least 10 units in length.

A common allele in RPGRIP1L is a modifier of retinal degeneration in ciliopathies.

Despite rapid advances in the identification of genes involved in disease, the predictive power of the genotype remains limited, in part owing to poorly understood effects of second-site modifiers. Here we demonstrate that a polymorphic coding variant of RPGRIP1L (retinitis pigmentosa GTPase regulator-interacting protein-1 like), a ciliary gene mutated in Meckel-Gruber (MKS) and Joubert (JBTS) syndromes, is associated with the development of retinal degeneration in individuals with ciliopathies caused by mutations in other genes. As part of our resequencing efforts of the ciliary proteome, we identified several putative loss-of-function RPGRIP1L mutations, including one common variant, A229T.

Recurrent Myocilin Asn480Lys glaucoma causative mutation arises de novo in a family of Andean descent.

Purpose: To search for MYOC mutations in Peruvian primary open angle glaucoma (POAG) families.

Patients And Methods: Two patients from each of the 11 POAG Peruvian families were screened for sequence variants in MYOC coding exons by conformational sensitive gel electrophoresis and sequencing was performed on the samples indicating probable sequence changes.

Results: We detected 2 families bearing distortions of conformational sensitive gel electrophoresis indicating mutations.