In silico analysis of novel mutations in maple syrup urine disease patients from Iran.

Maple Syrup Urine Disease (MSUD) is a rare autosomal recessive disorder of branched-chain amino acid (BCAA) metabolism. The disease is mainly caused by mutations either in the BCKDHA, BCKDHB, DBT or DLD genes encoding components of the E1α, E1ß, E2 and E3 subunits of branched-chain α-keto acid dehydrogenase complex (BCKDC), respectively. BCKDC is a mitochondrial enzyme which is responsible for the normal breakdown of BCAA. The rate of consanguineous marriage in Iran is 38.6 %, so the prevalence of autosomal recessive disorders is higher in comparison to other countries. Consanguinity increases the chance of the presence of pathogenic mutations in a homoallelic state. This phenomenon has made homozygosity mapping a powerful tool for finding the probable causative gene in heterogeneous disorders like IEM (Inborn Errors of Metabolism). In this study, two sets of multiplex polymorphic STR (Short Tandem Repeat) markers linked to the above-mentioned genes were selected to identify the probable pathogenic gene in the studied families. The families who showed a homozygous haplotype for the STR markers of the BCKDHB gene were subsequently sequenced. Four novel mutations including c.633 + 1G > A, c.988G > A, c.833_834insCAC, and a homozygous deletion of whole exon 3 c. (274 + 1_275-1) _(343 + 1_344-1), as well as one recently reported (c. 508G > T) mutation have been identified. Interestingly, three families shared a common haplotype structure along with the c. 508G > T mutation. Also, four other families revealed another similar haplotype with c.988G > A mutation. Founder effect can be a suggestive mechanism for the disease. Additionally, structural models of MSUD mutations have been performed to predict the pathogenesis of the newly identified variants.

FLT3 Gene Mutation Profile and Prognosis in Adult Acute Myeloid Leukemia.

BACKGROUND: Internal tandem duplication (ITD) of FMS-related tyrosine kinase 3 (FLT3) gene, which occurs in exons 14 and 15, is one of the most prevalent somatic mutations in adult acute myeloid leukemia (AML) and has biological, prognostic, and therapeutic implications. The prognostic importance of codon 835 tyrosine kinase domain (TKD) mutation (exon 20), which occurs relatively frequently in adult AML, is often debated. We aimed to study the FLT3 gene mutation profile and prognosis in 139 adult Iranian patients with newly diagnosed AML. METHODS: We determined the status of ITD and TKD mutations using fragment analysis and the polymerase chain reaction-restriction fragment polymorphism method, respectively. In addition, we used direct sequencing to confirm the results of TKD mutation analysis. RESULTS: Twenty five percent of the patients had an ITD mutation. The mean size of the inserted fragment was 63.5 base pairs. Twenty percent of the ITD-positive patients showed more than one mutated population upon polymerase chain reaction. Statistical analyses showed that the ITD mutation was associated with a decreased overall survival among patients in the intermediate cytogenetic risk group (p-value = 0.013). The size of the ITD was not correlated with overall survival. Eight out of 139 patients (5.7%) had the codon 835 mutation. One new mutation of the insertion/deletion type was discovered. Analyses did not show any relationship between the TKD mutation and overall survival. Two patients (1.4%) showed concurrent TKD and ITD mutations. The TKD and ITD mutation rates of the FLT3 gene were consistent with previous studies on AML patients. CONCLUSIONS: This study supports the results of previous studies regarding the association of the FLT3-ITD mutation and poor prognosis.