414B Poster - 05. Reproduction and gametogenesis
Friday April 08, 2:00 PM - 4:00 PM
A mutation in the gene for kinetochore protein Spc25 disrupts both homolog and sister chromatid connections in male meiosis and causes very high levels of meiosis I nondisjunction
Authors: Elsie Adams; Bruce McKee
Affiliation: University of Tennessee
Keywords: a. spermatogenesis; e. kinetochores and cohesion
Genetic and molecular analyses of ethyl-methanesulfonate (EMS) generated mutants has provided a solid forward genetics approach for discovering novel gene products and their roles in various mechanisms over many decades. Cytological analysis of the 3rd chromosome EMS mutant 122-044 strongly suggests a gene mutated plays role in mediating accurate connections, alignment and segregation patterns of chromosomes in both Drosophila male meiosis I and meiosis II. Fluorescence In Situ Hybridization (FISH) analysis with 3rd chromosome specific DNA probe Dodeca reveals 35% of mutant prometaphase I spermatocytes show loss of proper homolog conjunction (n=37), and 83% of mutant anaphase I divisions exhibit homolog nondisjunction of 3rd chromosome autosomes (n=30). Additionally, 20% of metaphase II mutant spermatocytes display premature sister chromatid separation (n=39). Efforts to map this mutated gene led gene candidates within identified a proximal euchromatic region on chromosome arm 3R. Sequencing of genomic DNA from one candidate, the kinetochore gene spc25, from 122-044 mutants revealed a potential 5’ splice site mutation predicted to generate a truncated Spc25 protein. The combination of our observed meiotic phenotypes appears to be novel in that proper chromosome segregation during meiosis I and II of male Drosophila has been understood to rely on two distinct mechanisms - homolog conjunction and sister chromatid cohesion, respectively. However, our understanding of the distinct roles of kinetochore protein complexes during Drosophila male meiosis is incomplete. Our study aims to better understand how specifically spc25 is involved in Drosophila male meiotic chromosome segregation as we complete gene specific complementation analyses, but also determine if some phenotypes may be attributed to mutations of additional genes.