Dataset Information

Novel homozygous mutations in Pakistani families with Charcot-Marie-Tooth disease.

ABSTRACT:

Background

Charcot-Marie-Tooth disease (CMT) is a group of genetically and clinically heterogeneous peripheral nervous system disorders. Few studies have identified genetic causes of CMT in the Pakistani patients.

Methods

This study was performed to identify pathogenic mutations in five consanguineous Pakistani CMT families negative for PMP22 duplication. Genomic screening was performed by application of whole exome sequencing.

Results

We identified five pathogenic or likely pathogenic homozygous mutations in four genes: c.2599C > T (p.Gln867*) and c.3650G > A (p.Gly1217Asp) in SH3TC2, c.19C > T (p.Arg7*) in HK1, c.247delG (p.Gly83Alafs*44) in REEP1, and c.334G > A (p.Val112Met) in MFN2. These mutations have not been reported in CMT patients. Mutations in SH3TC2, HK1, REEP1, and MFN2 have been reported to be associated with CMT4C, CMT4G, dHMN5B (DSMA5B), and CMT2A, respectively. The genotype-phenotype correlations were confirmed in all the examined families. We also confirmed that both alleles from the homozygous variants originated from a single ancestor using homozygosity mapping.

Conclusions

This study found five novel mutations as the underlying causes of CMT. Pathogenic mutations in SH3TC2, HK1, and REEP1 have been reported rarely in other populations, suggesting ethnic-specific distribution. This study would be useful for the exact molecular diagnosis and treatment of CMT in Pakistani patients.

SUBMITTER: Kanwal S

PROVIDER: S-EPMC8247155 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND: The identification of disease causing, or putative disease causing, mutations in index patients with Charcot-Marie-Tooth disease (CMT) allows for genetic testing of family members. Relevant variants identified in index patients are of either definite, likely or uncertain pathogenicity. The main objective of this study was to make an evaluation of the family investigations performed as part of the assessment of genetic variants of unknown clinical significance (VUS). METHODS: Between 2004 and 2010 molecular genetic family investigations were requested for 87 family members from 41 families harbouring PMP22dup or genetic variants in GJB1, MPZ, MFN2 and NEFL. Relatives were tested for the family mutation and data from the requisitions were evaluated by means of statistical tools. RESULTS: The results within each indication category are presented and discussed in detail. Twenty-two relatives (9 affected) from eight families were included in the segregation analyses, which invoked reclassification of three MFN2 mutations, two of which were de novo substitutions (c.2146_2148dup, c.692C > T). One MFN2 substitution was downgraded due to non-segregation (c.1709 A > G), and a MPZ substitution (c.103 G > A) upgraded due to segregation with the phenotype in the family. CONCLUSIONS: The results allow for the evaluation of the patient phenotypes ascertained in families, as opposed to the phenotypic descriptions of index patients. They indicate that de novo MFN2 mutations are regularly found in patients with a classical CMT2 phenotype. They also demonstrate the importance of a precise clinical and neurophysiologic diagnosis of affected family members. This particularly applies for the examination of variants of uncertain clinical significance. Finally, the fact that 14,6% of affected relatives tested for (probable or certain) pathogenic mutations were mutation negative, demonstrates that clinical evaluation alone is not always sufficient in order to determine their diagnosis. We believe that the results will aid in the estimation and planning of resources required for the various aspects of family evaluations in CMT.