Dana Šafka Brožková

Role of estrogen related receptor beta (ESRRB) in DFN35B hearing impairment and dental decay.

BackgroundCongenital forms of hearing impairment can be caused by mutations in the estrogen related receptor beta (ESRRB) gene. Our initial linkage studies suggested the ESRRB locus is linked to high caries experience in humans.MethodsWe tested for association between the ESRRB locus and dental caries in 1,731 subjects, if ESRRB was expressed in whole saliva, if ESRRB was associated with the microhardness of the dental enamel, and if ESRRB was expressed during enamel development of mice.ResultsTwo families with recessive ESRRB mutations and DFNB35 hearing impairment showed more extensive dental destruction by caries. Expression levels of ESRRB in whole saliva samples showed differences depending on sex and dental caries experience.ConclusionsThe common etiology of dental caries and hearing impairment provides a venue to assist in the identification of individuals at risk to either condition and provides options for the development of new caries prevention strategies, if the associated ESRRB genetic variants are correlated with efficacy.

Six new gap junction beta 1 gene mutations and their phenotypic expression in Czech patients with Charcot-Marie-Tooth disease.

X-linked Charcot-Marie-Tooth (CMTX) disease is a hereditary motor and sensory neuropathy caused by mutations in the gap junction beta 1 gene (GJB1 codes for connexin 32). In this study we report six novel mutations p.Met1Arg, p.Leu9Phe, p.Ser17Tyr, p.Val63Phe, p.Val170Ile, and p.Leu212Phe in GJB1 and their phenotypic expression. These mutations affect both intracellular and extracellular parts of the GJB1 protein. The screened patients had previously excluded the duplication/deletion on 17p11.2 and the male-to-male transfer in the pedigree. Except p.Val170Ile, all reported mutations segregated with the CMT phenotype in the families and caused CMTX1 neuropathy. Mutations were not found in 200 control DNA samples. Additionally, we performed in silico analysis of the novel mutations with the program PANTHER. The PANTHER scored five mutations, all but p.Val170Ile, as likely deleterious and supported the pathogenicity of the found mutations. These results provided evidence that these five mutations are causative for CMTX1.

Severe axonal Charcot-Marie-Tooth disease with proximal weakness caused by de novo mutation in the MORC2 gene

Sir, It was with great interest that we read the article on advanced access by Sevilla et al. (2015) regarding axonal Charcot-Marie-Tooth (CMT2) disease caused by mutations in the MORC2 gene. Through whole-exome sequencing in a Spanish four generation CMT2 family with autosomal dominant pattern of inheritance, the authors identified the mutation p.R190W in the MORC2 gene as the cause of the disease. It was the only variant detected by whole-exome sequencing that segregated with the disease in the family. Afterwards, they tested an additional 52 patients with axonal Charcot-Marie-Tooth and found mutations in the MORC2 gene in two additional families, one with different de novo mutation and the second with the same p.R190W mutation, also de novo. Here, we would like to report another patient with the p.R190W mutation in the MORC2 gene and thus confirm the causality of this gene for the severe CMT2 with striking proximal weakness. Also, we would like to show that the p.R190W mutation is a hot spot and probably the most frequent mutation in this gene. Immediately after we became aware of this newly discovered gene, we detected this mutation by re-examining older whole-exome sequencing data in one of …

Spectrum and frequencies of mutations in the MFN2 gene and its phenotypical expression in Czech hereditary motor and sensory neuropathy type II patients

The axonal type of Charcot‑Marie‑Tooth (CMT) disorders is genetically heterogeneous, therefore the causal mutation is unlikely to be observed, even in clinically well characterized patients. Mitofusin‑2 (MFN2) gene mutations are the most frequent cause of axonal CMT disorders in a number of populations. There are two phenotypes; early onset, which is severe and late onset, which is a milder phenotype. A cohort of 139 unrelated Czech patients with axonal neuropathy was selected for sequencing and multiplex ligation-dependent probe amplification analysis (MLPA) testing of the MFN2 gene. A total of 11 MFN2 mutations were detected, with eight pathogenic mutations and three potentially rare benign polymorphisms. MLPA testing in 64 unrelated patients did not detect any exon duplication or deletion. The frequency of the pathogenic mutations detected in Czech hereditary motor and sensory neuropathy type II (HMSN II) patients was 7.2%. Early onset was more frequent among pathogenic mutation cases. Therefore we propose to examine the MFN2 gene mainly in patients with early and severe axonal CMT.

DFNB35 due to a novel mutation in the ESRRB gene in a Czech consanguineous family

OBJECTIVES Non-syndromic hearing loss (NSHL) is a genetically heterogeneous disorder with mostly autosomal recessive inheritance. So far 40 genes and the same amount of loci with as yet unknown genes were described with autosomal recessive NSHL. PATIENTS AND METHODS A consanguineous Czech family with a child with NSHL was genotyped using SNP array and homozygous regions were compared with previously reported DFNB loci. RESULTS GRXCR1 and ESRRB genes associated with autosomal recessive NSHL were located in two of the eight homozygous regions detected by SNP array genotyping. Mutation p.R291L in a homozygous state was found in the deaf child, the parents were heterozygous. The entire coding region of the ESRRB gene was sequenced in additional 39 patients of Czech origin with early NSHL and only two variants, p.V413I and p.P386S, were found in homozygous state, but are considered to be polymorphisms. CONCLUSION Homozygosity mapping is a powerful method for identification of genes in heterogeneous recessive diseases. This is the first report of DFNB35 mutations in the Czech Republic and it seems to be a rare cause of NSHL. Additional mutations in ESRRB gene were reported in Pakistan, Tunisia and Turkey.

Mutations in eight small DFNB genes are not a frequent cause of non-syndromic hereditary hearing loss in Czech patients

OBJECTIVES To evaluate the contribution of eight small NSHL-AR (non-syndromic deafness, autosomal recessive) genes to hereditary hearing loss in Czech patients. PATIENTS AND METHODS Unrelated Czech patients, adults and children, diagnosed with pre-lingual hereditary hearing loss with at least one similarly affected deaf sibling and with previously excluded mutations in the GJB2 gene were investigated by Sanger sequencing of the selected eight small NSHL-AR associated genes (CABP2 - 51 patients, CIB2 - 45 patients, PJVK/DFNB59 - 53 patients, GJB3 - 46 patients, ILDR1 - 48 patients, LHFPL5 - 66 patients, LRTOMT - 60 patients, TMIE - 64 patients). RESULTS Mutations were detected in the LHFPL5 (DFNB67) gene. The patient is heterozygote for two already described pathogenic variants (p.Tyr127Cys, p.Thr165Met). In five samples, five rare heterozygous variants (two novel) predicted as pathogenic were detected in genes CABP2, ILDR1, LHFPL5 and LRTOMT. CONCLUSION Mutations in eight small NSHL-AR genes are not a frequent cause of hereditary hearing loss in the Czech Republic. This diagnostic approach permitted the clarification of HL in only one patient - two heterozygous mutations were detected in LHFPL5 gene for the first time in Central Europe. As the use of panel base MPS certainly improves the diagnostic yield, future studies should rather profit from that diagnostic strategy.

Czech family confirms the link between FBLN5 and Charcot–Marie–Tooth type 1 neuropathy

Sir, The article by Auer-Grumbach et al. (2011) reporting that fibulin 5 ( FBLN5 ) mutations are also linked to inherited neuropathies helped us to clarify the cause of autosomal dominant, demyelinating hereditary motor and sensory neuropathy (HMSN I) in our long-time known, but unsolved, Czech family. Before this study was published, mutations in FBLN5 were associated only with the connective tissue disorder cutis laxa (Loeys et al. , 2002; Markova et al. , 2003; Lotery et al. , 2006; Nascimento et al. , 2010) and age-related macular degeneration leading to vision loss in those aged >50 years (Stone et al. , 2004; Lotery et al. , 2006). Auer-Grumbach et al. (2011) were the first to describe a large family with demyelinating Charcot–Marie–Tooth (CMT1) and linkage with the interval on chromosome 14. Subsequent resequencing of this region revealed only one novel variant c.1117 C > T (p.R373C) segregating with the disease in the family. Additional screening of 112 patients with Charcot–Marie–Tooth disease showed two other sequence variations in two patients with pure motor neuropathy and hyperelastic skin. The linkage with log of odds score >3.31 indicates the FBLN5 mutation as highly probably causal for HMSN I, but no functional study to confirm this was performed, and no other study on FBLN5 mutations in a family with HMSN has been published to date. This Austrian HMSN I family is the only one reported worldwide. We report a second family with non-syndromic inherited demyelinating motor and sensory neuropathy (HMSN I) with FBLN5 mutation and confirm FBLN5 mutations as the new cause of HMSN I. We used exome sequencing for clarification of the cause of HMSN I in a Czech family recruited in 2001 (Fig. 1A). The most frequent causes of CMT1 (CMT1 duplication/HNPP …

Charcot-Marie-Tooth neuropathy due to a novel EGR2 gene mutation with mild phenotype--usefulness of human mapping chip linkage analysis in a Czech family.

Charcot-Marie-Tooth neuropathies (CMT) are a group of clinically and genetically heterogeneous disorders of the peripheral nervous system. Selection of candidate disease genes for mutation analysis is sometimes difficult since more than 40 genes and loci are known to be associated with CMT neuropathies. Hence a Czech family Cz-CMT with demyelinating type of autosomal dominant CMT disease was investigated by genome-wide linkage analysis by means of single-nucleotide polymorphism (SNP) arrays. Among 35 regions with linkage, five carried known CMT genes. In the final result a novel early growth response 2 - missense mutation c.1235 A>G, p.Glu412Gly was found. Surprisingly, the more severely affected proband carried an additional heterozygous myelin protein zero variant p.Asp246Asn detected previously, which may modify the phenotype. However, this MPZ variant is benign in heterozygous state alone, because it is also carried by the patients healthy father.

Four novel point mutations in the PMP22 gene with phenotypes of HNPP and Dejerine-Sottas neuropathy.

We report four novel point mutations in the PMP22 gene with two different phenotypes: mutation p.Ser79Thr arose de novo in a patient with the Dejerine–Sottas neuropathy (DSN) phenotype; and mutations c.78+5 G>A, c.320‐1 G>C, and p.Trp140Stop segregated with HNPP in 5 families.Our findings show that point mutations in PMP22 may be more likely in HNPP patients than in CMT1 patients after exclusion of CMT1A/HNPP. Muscle Nerve, 2011

HMSN Lom in 12 Czech patients, with one unusual case due to uniparental isodisomy of chromosome 8

Hereditary motor and sensory neuropathy-type Lom (HMSNL), also known as CMT4D, a demyelinating neuropathy with late-onset deafness is an autosomal recessive disorder threatening Roma population worldwide. The clinical phenotype was reported in several case reports before the gene discovery. HMSNL is caused by a homozygous founder mutation p.Arg148* in the N-Myc downstream-regulated gene 1. Here, we report findings from the Czech Republic, where HMSNL was found in 12 Czech patients from eight families. In these 12 patients, 11 of the causes were due to p.Arg148* mutation inherited from both parents by the autosomal recessive mechanism. But in one case, the recessive mutation was inherited only from one parent (father) and unmasked owing to an uniparental isodisomy of the entire chromosome eight. The inherited peripheral neuropathy owing to an isodisomy of the whole chromosome pointed to an interesting, less frequent possibility of recessive disease and complications with genetic counseling.