Is population frequency a useful criterion to assign pathogenicity to newly described mitochondrial DNA variants?

Population frequency has been one of the most widely used criteria to help assign pathogenicity to newly described mitochondrial DNA variants. However, after sequencing this molecule in thousands of healthy individuals, it has been observed that a very large number of genetic variants have a very low population frequency, which has raised doubts about the utility of this criterion. By analyzing the genetic variation of mitochondrial DNA-encoded genes for oxidative phosphorylation subunits in 195,983 individuals from HelixMTdb that were not sequenced based on any medical phenotype, we show that rare variants are deleterious and, along with other criteria, population frequency is still a useful criterion to assign pathogenicity to newly described variants

Food derived respiratory complex I inhibitors modify the effect of Leber hereditary optic neuropathy mutations

Mitochondrial DNA mutations in genes encoding respiratory complex I polypeptides can cause Leber hereditary optic neuropathy. Toxics affecting oxidative phosphorylation system can also cause mitochondrial optic neuropathy. Some complex I inhibitors found in edible plants might differentially interact with these pathologic mutations and modify their penetrance. To analyze this interaction, we have compared the effect of rotenone, capsaicin and rolliniastatin-1 on cybrids harboring the most frequent Leber hereditary optic neuropathy mutations and found that m.3460G > A mutation increases rotenone resistance but capsaicin and rolliniastatin-1 susceptibility. Thus, to explain the pathogenicity of mitochondrial diseases due to mitochondrial DNA mutations, their potential interactions with environment factors will have to be considered

Effective Utilization of Molecular Genetic Screening of Patients with Sickle Cell Disease and Beta Thalassemia Major in Saudi Arabia

Hereditary blood diseases are prevalent in the Kingdom of Saudi Arabia. The majority of these blood disorders are sickle cell disease and β-thalassemia with variants located on the beta globin gene (HBB). Aim: To determine the profile of novel or previously reported causative mutations in more than 150 transfusion dependent individuals using TaqMan genotyping and next-generation DNA sequencing. In addition, I explored the genomic variation in a family with transfusion dependency but without a definitive genetic diagnosis related to HBB. I also attempted to detect unknown genetic variations in functionally related genes and applied in-silico analysis of the detected variants to propose candidate genes that may contribute to the severe etiology of thalassemia within a family. Methods: To identify HBB variants, I conducted Taqman genotyping tests using SCD, c.92+5G>C, c.92+1G>A, c.93-21G>A, c.27dupG, and c.118C>T as the most frequently identified HBB variants within the Saudi population. After that, targeted next generation sequencing was performed on samples with either negative or only heterozygous results for these variants. The use of different molecular techniques including MLPA alpha thalassemia, whole exome sequencing, cytoscan HD array, and whole genome sequencing was undertaken on samples that needed further investigation. Implementation of different data filtering approaches and several in-silico techniques were utilized to investigate the detected variants. Results: After Taqman genotyping of the 154 DNA samples, 100 samples were either homozygous or compound heterozygous for the most frequently known HBB variants. The rest of these samples were sequenced using targeted NGS and 20 different common and rare HBB variants were identified. Three out of the 154 samples did not have any apparent HBB mutation and further investigation was applied using additional molecular techniques. This led to the identification of two gene candidates, SMC5 and TALDO1, with possible novel associations in increasing the severity of clinical manifestation in transfusion-dependent patients with heterozygous pathogenic variant of beta thalassemia. Conclusion: Beta thalassemia is a heterogenous disease with a wide range of clinical severity and the steps towards identification of the underlying genetic cause of the phenotype is different from case to case and may require a combination of several molecular techniques. Therefore, the interaction of illness-causing variations with the rest of an individual's genome is crucial to gaining a complete understanding of the condition. Excellent detection rates in less time may be achieved with a specialized filtering technique and strategy, making this an option for primary laboratory workflow

Psr1p interacts with SUN/sad1p and EB1/mal3p to establish the bipolar spindle

Regular Abstracts - Sunday Poster Presentations: no. 382During mitosis, interpolar microtubules from two spindle pole bodies (SPBs) interdigitate to create an antiparallel microtubule array for accommodating numerous regulatory proteins. Among these proteins, the kinesin-5 cut7p/Eg5 is the key player responsible for sliding apart antiparallel microtubules and thus helps in establishing the bipolar spindle. At the onset of mitosis, two SPBs are adjacent to one another with most microtubules running nearly parallel toward the nuclear envelope, creating an unfavorable microtubule configuration for the kinesin-5 kinesins. Therefore, how the cell organizes the antiparallel microtubule array in the first place at mitotic onset remains enigmatic. Here, we show that a novel protein psrp1p localizes to the SPB and plays a key role in organizing the antiparallel microtubule array. The absence of psr1+ leads to a transient monopolar spindle and massive chromosome loss. Further functional characterization demonstrates that psr1p is recruited to the SPB through interaction with the conserved SUN protein sad1p and that psr1p physically interacts with the conserved microtubule plus tip protein mal3p/EB1. These results suggest a model that psr1p serves as a linking protein between sad1p/SUN and mal3p/EB1 to allow microtubule plus ends to be coupled to the SPBs for organization of an antiparallel microtubule array. Thus, we conclude that psr1p is involved in organizing the antiparallel microtubule array in the first place at mitosis onset by interaction with SUN/sad1p and EB1/mal3p, thereby establishing the bipolar spindle.postprin