Synaptic behavior of Leptodactylus pentadactylus (Anura: Leptodactylidae) by immunolocalization of proteins

Abstract

Most species of the genus Leptodactylus share similar karyotypes, with 2n=22 and NF=44. The species L. pentadactylus presents a multivalent in its karyotype, resulting from multiple translocations, forming a ring chromosome during meiosis I. In this study analyzed the meiotic behavior of L. pentadactylus, from Brazilian Amazonia, through immunoprotein markers. Testicular tissues of an adult male were collected and analyzed by immunofluorescence microscopy, using antibodies to detect the following meiotic proteins: SMC3, component of chromosomal axis, and responsible for cohesion between sister chromatids; ?-H2AX in a protein marker of meiotic silencing of unsynapsed chromatin (MSUC). The results showed that: in leptotene, SMC3 and ?-H2AX mark fuzzy segments throughout all the chromatin; in the zygotene; regions that start synapses are intensely marked by ?-H2AX; in turn, with the advancement of the synapse at the end of the zygotene, ?-H2AX markings expand evenly in the chromatin; in pachytene, the synapsis remains incomplete, and several asynaptic regions were noted, with ?-H2AX markings more intense on synapsed regions of chromosomes involved or not in multivalent links; in diplotene, the synaptonemal complex is disorganized, SMC3 cohesin is present on partially decondensed, chromatin, and ?-H2AX markings are present only in some regions; in diakinesis, SMC3 maintains the same pattern of diplotene, however, ?-H2AX markings are quite reduced. The results of meiotic behavior of L. pentadactylus show asynaptic axes in pachytene, which probably do not present homology with each other, corresponding to segments that suffered multiple rearrangements. SMC3 pattern and reduction of ?-H2AX markings in diplotene, suggest decondensation of chromatin, with reactivation of transcription in chromosomal handles. The absence of ?-H2AX markings in diakinesis show that the rearranged chromosomes of L. pentadactylus do not compromise the spermatogenesis of the animal, ensuring its meiotic dynamic and fertility.