Browsing by Author "Junna, Nella"

Charcot-Marie-Tooth disease is a clinically and genetically heterogeneous group of disorders of the peripheral nervous system. It affects both peripheral motor and sensory nerves that lead to progressive degeneration of muscles in the lower limbs. Prevalence of CMT is 1:2500. It can be divided into two groups: CMT1 is the demyelinating type and CMT2 is the axonal type. There are 20 known genes associated with CMT2 but not all of them have been found yet. Hereditary spastic paraplegia (HSP) is a group of inherited neurological disorders and it is also genetically and clinically heterogeneous. HSP is caused by degeneration of the upper motor neurons in the brain and spinal cord. HSP can be divided into pure and complex forms. In pure forms the main symptoms are progressive spasticity and weakness in the lower limbs. In complex forms there are additional symptoms such as epilepsy and mental retardation. The prevalence of HSP is 2-10:100 000. There are over 70 loci associated with HSP and 55 genes identified so far but there is probably more to be found. With both of these diseases it has been difficult to diagnose patients at the genetic level because of the great amount of disease genes. The aim of this study was to identify potential disease causing mutations by using targeted next-generation sequencing (NGS) and also to do functional testing with the discovered mutations. There were 48 patients, 28 diagnosed with CMT and 20 with HSP. For the targeted sequencing there was a gene panel with 167 genes, including genes associated with neuropathy, paraplegia, ALS and mitochondrial functions. Analyzing of the gene variants was largely based on their frequencies in the population and several exome databases were used. All possibly pathogenic mutations were confirmed with Sanger-sequencing and also sequenced from the patients’ relatives, if DNA samples were available. Possible genetic diagnosis was found for five CMT patients and six HSP patients. Only one of the mutations was previously known. One of the probably pathogenic mutations was a deletion, others were missense mutations. Large portion of the patients were left without a genetic diagnosis probably because there are many more genes associated with these diseases to be found. De novo heterozygous missense mutations in the KIF1A gene were found to cause a novel phenotype. Symptoms of these patients include classical HSP symptoms and additionally intellectual disability and other symptoms, such as cerebellar atrophy, in some patients. In this study we found a deletion in the gene HSPB1 that causes premature STOP codon that leads to disappearance of nearly the entire C-terminus. In this study I built a HSPB1-Western blot assay that was used in further research. It was found out that the truncated protein was stabile, it forms dimers with the normal protein and impairs the cells response against stress caused by misfolded proteins.