Microdissection and complete sequencing of B chromosomes in fish applied to functional and evolutionary studies

Abstract

B chromosomes are genomic elements extra from normal chromosomes (A chromosomes) and occur in many organisms. They may have different origin, including derivation of autosomal chromosomes, sex chromosomes and even from cross-species hibridization. The molecular mechanisms that guide the evolution of these genomic segments are similar to the univalente sex chromosomes and may involve gene silencing, heterochromatinization process and transposons. The advent of microdissection technique, method that allows the direct isolation of DNA from any chromosome region, has promoted advances in the knowledge of structure and composition of these genomic elements in a significant number of organisms that possess B chromosomes. The present study is inserted in the general Project of cytogenetic and molecular genetic studies of Neotropical fishes under development in the Laboratório de Biologia e Genética de Peixes (IBB/UNESP/BOTUCATU) and its main objective is the identification of sequences alocated in the B chromosomes, euchromatic and heterochromatic, of the fish species Moenkhausia sanctaefilomenae. This Project will be based on the microdissection of B chromosomes of this species and its complete sequencing by 454 Jr. (Roche) platform. The development of this work will show the molecular content of these B chromosomes, which includes the description of genes, repetitive families and transposable elements allocated in these genomic elements. With the results obtained, it is intended to increase the knowledge about the structure and molecular composition of these chromosomes, as well as deduce about the possible origin and functionality of the sequences found. (AU)