Analysis of chromosomal polymorphism in Mazama gouazoubira (Artiodactyla; Cervidae): implications for cervidae karyotype evolution

Author(s)

Iara Maluf Tomazella

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2017-01-18.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2016-12-01
• Advisor: José Maurício Barbanti Duarte

Abstract

Mazama gouazoubira (2n = 70; FN = 70), popylarly known as brown brocket deer, is known to have chromosomal fragility, which is responsible for intraspecific chromosome variation, characterized by the presence of Robertsonian translocations and B chromosomes. There are no data of the location of the chromosome regions involved in rearrangements of M. gouazoubira and the possible existence of fragile sites (FSs) in points where breaks occur. Thus, it is necessary to evaluate the chromosomal polymorphism presented by this species and to identify the FSs, investigating the relationship between FSs and polymorphism. Were analyzed 135 animals, of which 68 (50.37%) were variant individuals, 47 animals (69.12%) had B chromosomes, six animals (8.82%) were heterozygous for a Robertsonian translocation, one individual (1.47%) was homozygous for a Robertsonian translocation, 14 animals (20.59%) presented both B chromosomes and heterozygotes for a Robertsonian translocation. Were identified seven different types of translocations (X;16, X;21, 4;16, 14;16, 7;21, 20;26, 8;21) involving nine different chromosomes. X-autosomal translocations were confirmed by C-banding, Ag-NOR staining, Fluorescence in situ hybridization (FISH) with telomeric probes and chromosome painting with X chromosome-specific probe. A large variability of B chromosomes was observed among the analyzed individuals. These chromosomes were highly heterogeneous in relation to pattern of heterochromatin distribution, presence and amount of rDNA in nucleolar organizer region (NOR), lozalization of telomeric sequences and homologies between chromosome complements A and B. Aphidicolin was an efficient inducer of common fragile sites (CFSs), showing the occurrence of CFSs in gaps and breaks, both chromatid and chromosomal. The G-banding located 531 CFSs distributed in 18 chromosome pairs (X, 1, 2, 4, 5, 6, 7, 8, 10, 11, 13, 14, 16, 17, 18, 21, 22 and 34). It was found that the most CFSs are localized at the boundaries between the bright bands and dark bands. The different rates of CFSs presented by each chromosome showed that some chromosome pairs are more fragile than others. Of the 18 chromosomes pais with CFSs, seven are related to the Robertsonian translocations observed in brown brocket deer, and only one chromosome involved with polymorphism does not have CFSs. Thus, the chromosomal polymorphism presented by M. gouazoubira may be related to chromosomal fragility. It is necessary to deepen the studies to understand the impact of this polymorphism on the Brazilian population of brown brocket deer. (AU)

• FAPESP's process: 13/06100-7 - Analysis of chromosomal polymorphism in Mazama gouazoubira (Artiodactyla; Cervidae); implications for karyotype evolution in Cervidae.
• Grantee: Iara Maluf Tomazella
• Support Opportunities: Scholarships in Brazil - Doctorate