Abstract Rodentia has a high species number and chromosomal variability. The South American genus Akodon is one of the most speciose muroids, with more than 40 species included in several species groups. Here, we characterize cytogenetically specimens of Akodon from central-western Argentina. Subsequently, we reviewed and analyzed the cytogenetic data for this genus, build a phylogeny and mapped chromosome changes to interpret its evolution. Specimens of A. dolores from central-western Argentina have 2n=42-44/FNa=44 (46, 48) due to a Robertsonian rearrangement. Our data expand the distribution range known for this polymorphism and confirm its geographic structure. Other specimens had 2n=40/FNa=40, representing populations of A. oenos, A. polopi, and A. spegazzinii. All karyotypes have a low amount of heterochromatin, concentrated in centromeres and sex chromosomes, as in other rodents. The complement with 2n=40/FNa=40 is the most frequent in Akodon and is shared by most species in some groups. Chromosome numbers are very diverse. The FNa shows less variability; FNa=42 was recovered as ancestral, excluding A. mimus, which was connected at the base of the Akodon tree and has FNa=44. This indicates a complex chromosome evolution in Akodon, and suggests that reductions and increases in the 2n and FNa evolved independently in some lineages.

During the past 20 years, the Laboratory of Cytogenetics and Mutagenesis at IMBICE has developed various studies to analyze the genotoxicity caused by different chemical mutagens to eukaryotic cells. Research has mainly focused on the analysis of the genotoxic mechanisms involved and the effects caused by three antibiotics of known antitumor properties, bleomycin (BLM), streptonigrin (EN), and streptozotocin (EZ). Several cell lines and human peripheral blood lymphocytes were used as experimental models. Currently, our studies are devoted to analyze the effects of those antibiotics on telomeres and interstitial telomeric sequences of vertebrate chromosomes. Since BLM and EN exert direct damage on DNA and chromosomes by free radicals release, these antibiotics are considered radiomimetic compounds. EZ is frequently used to induce diabetes mellitus in laboratory rats, and though it exerts its genotoxic action partially by free radical release, in contrast to BLM and EN, it is an alkylating agent. The present work summarizes the most significant results obtained during the last 15 years by the research group at the Laboratory of Cytogenetics and Mutagenesis (IMBICE) on the genotoxic effects of the antibiotics above mentioned.

En el Laboratorio de Citogenética y Mutagénesis del IMBICE, se llevan a cabo desde hace más de 20 años estudios tendientes a analizar la genotoxicidad de diversos mutágenos químicos en células eucariotas. En este contexto, las investigaciones han estado centradas principalmente en el análisis de los efectos genotóxicos de tres antibióticos que poseen propiedades antitumorales, la bleomicina (BLM), la estreptonigrina (EN) y la estreptozotocina (EZ) sobre células de mamífero e insecto y de los mecanismos involucrados en la genotoxicidad inducida por dichos compuestos. Los estudios fueron realizados utilizando diversas líneas celulares y linfocitos de sangre periférica humana como modelos experimentales. En la actualidad, las investigaciones están orientadas a analizar los efectos de los antibióticos antemencionados sobre los telómeros y secuencias teloméricas intersticiales de los cromosomas de vertebrados. La BLM y la EN son considerados compuestos radiomiméticos por su capacidad de ejercer daño directo en el ADN y cromosomas a través de la generación de radicales libres. Por otra parte, la EZ es un antibiótico comúnmente utilizado para inducir diabetes mellitus en ratas de laboratorio y, si bien ejerce su acción genotóxica parcialmente mediante la liberación de radicales libres, a diferencia de la BLM y la EN, es un agente alquilante. En este trabajo, se resumen los principales resultados obtenidos en los últimos 15 años en el Laboratorio de Citogenética y Mutagénesis del IMBICE acerca de los efectos genotóxicos de los antibióticos mencionados.