Identificação e caracterização de transcritos associados ao desenvolvimento e crescimento da musculatura esquelética em frangos (Gallus gallus)

Abstract

Identification and characterization of transcripts associated with skeletal muscle development and growth in chicken (Gallus gallus). A large improvement in skeletal muscle mass quantity in domestic animals was achieved by animal breeding programs along the years based on the observation of adult phenotypic characters. But, the number of myogenic precursor cells and, consequently, the number of muscle fibers is determined during the embryonic stages of development. Therefore, the embryonic myogenic program is an ideal target for searching potential candidate-transcripts, that can influence skeletal muscle deposition in domestic animals. This work aimed to identify original candidate-transcripts associated with skeletal muscle development and growth in chicken embryos (Gallus gallus). A total of previously identified 4,534 transcripts (Expressed Sequence Tags) were transferred to a nylon membrane (microarray) to investigate differences in expression patterns among genotypes and tissues. The pectoral skeletal muscle transcriptional pattern between broiler and layer chicken lines allowed the identification of 98 differentially expressed transcripts, whose expression were validated by quantitative RT-PCR (Reverse-transcription Polymerase Chain Reaction), and were co-localized in coincident regions with previously mapped QTLs (Quantitative Trait Loci). These transcripts are now preferential candidates to further identify mutations, and/or to develop specific markers to be used in breeding programs for early or indirect selection of superior animals. The same microarray was used to characterize unknown transcripts by expression patterns among five tissues (brain, heart, liver, muscle and skin). This approach allowed to identify tissue-specific and/or preferentially-expressed transcripts, and to characterize 24 unknown transcripts as co-expressed with skeletal musclespecific ones. Finally, the axon guidance molecule RGM-A, identified as skeletal muscle-specific transcript by microarrays, was selected to be functionally analyzed in vivo, to investigate the function of this atypical transcript in the skeletal muscle and to demonstrate the approach efficiency to guide selection of candidate transcripts. The RGM-A expression pattern and the Pax3 phenotype after over-expression in chicken embryos indicated a possible association of this axon guidance with the skeletal muscle formation. The candidate transcripts identified by mycroarray analyses may be useful in animal breeding programs to increase the present gains in chicken growth rate, since additional information is urgently required to surpass current limits of selection gains. The results have also opened a new range of possibilities to promote the functional characterization in vivo of unknown transcripts, having chicken embryos as models.

Caracterização da expressão da Miostatina e de seus reguladores ao longo da miogênese esquelética de galinha (Gallus gallus) /

“…Somado a questão evolutiva, especificamente os frangos se constituem como o principal representante de aproximadamente 9.600 espécies de aves (HILLIER et al, 2004). A espécie Gallus gallus têm sido amplamente utilizada como um organismo-modelo para estudos de diversos aspectos e sistema biológicos e devido a sua importância biológica e econômica, essa espécie foi a primeira a ter o sequenciamento do seu genoma determinado (HILLIER et al, 2004;JORGE, 2006).…”