RESUMO
BACKGROUND: The developmental transition between the late fetus and a newborn animal is associated with profound changes in skeletal muscle function as it adapts to the new physiological demands of locomotion and postural support against gravity. The mechanisms underpinning this adaption process are unclear but are likely to be initiated by changes in hormone levels. We tested the hypothesis that this developmental transition is associated with large coordinated changes in the transcription of skeletal muscle genes. RESULTS: Using an ovine model, transcriptional profiling was performed on Longissimus dorsi skeletal muscle taken at three fetal developmental time points (80, 100 and 120 d of fetal development) and two postnatal time points, one approximately 3 days postpartum and a second at 3 months of age. The developmental time course was dominated by large changes in expression of 2,471 genes during the interval between late fetal development (120 d fetal development) and 1-3 days postpartum. Analysis of the functions of genes that were uniquely up-regulated in this interval showed strong enrichment for oxidative metabolism and the tricarboxylic acid cycle indicating enhanced mitochondrial activity. Histological examination of tissues from these developmental time points directly confirmed a marked increase in mitochondrial activity between the late fetal and early postnatal samples. The promoters of genes that were up-regulated during this fetal to neonatal transition were enriched for estrogen receptor 1 and estrogen related receptor alpha cis-regulatory motifs. The genes down-regulated during this interval highlighted de-emphasis of an array of functions including Wnt signaling, cell adhesion and differentiation. There were also changes in gene expression prior to this late fetal--postnatal transition and between the two postnatal time points. The former genes were enriched for functions involving the extracellular matrix and immune response while the latter principally involved functions associated with transcriptional regulation of metabolic processes. CONCLUSIONS: It is concluded that during late skeletal muscle development there are substantial and coordinated changes in the transcription of a large number of genes many of which are probably triggered by increased estrogen levels. These changes probably underpin the adaption of muscle to new physiological demands in the postnatal environment.
Assuntos
Redes Reguladoras de Genes/genética , Músculo Esquelético/metabolismo , Ovinos/embriologia , Ovinos/genética , Animais , Sequência Conservada , Cães , Feminino , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Masculino , Camundongos , Fibras Musculares Esqueléticas/metabolismo , Músculo Esquelético/crescimento & desenvolvimento , Oxirredução , Ratos , Sequências Reguladoras de Ácido Nucleico/genética , Ovinos/crescimento & desenvolvimento , Fatores de Tempo , Transcrição GênicaRESUMO
A comprehensive physical map was generated for Ovis aries chromosome X (OARX) based on a cytogenomics approach. DNA probes were prepared from bacterial artificial chromosome (BAC) clones from the CHORI-243 sheep library and were assigned to G-banded metaphase spreads via fluorescence in-situ hybridization (FISH). A total of 22 BACs gave a single hybridization signal to the X chromosome and were assigned out of 32 tested. The positioned BACs contained 16 genes and a microsatellite marker which represent new cytogenetically mapped loci in the sheep genome. The gene and microsatellite loci serve to anchor between the existing radiation hybrid (RH) and virtual sheep genome (VSG) maps to the cytogenetic OARX map, whilst the BACs themselves also serve as anchors between the VSG and the cytogenetic maps. An additional 17 links between the RH and cytogenetic maps are provided by BAC end sequence (BES) derived markers that have also been positioned on the RH map. Comparison of the map orders for the cytogenetic, RH, and virtual maps reveals that the orders for the cytogenetic and RH maps are most similar, with only one locus, represented by BAC CH243-330E18, mapping to relatively different positions. Several discrepancies, including an inverted segment are found when comparing both the cytogenetic and RH maps with the virtual map. These discrepancies highlight the value of using physical mapping methods to inform the process of future in silico map construction. A detailed comparative analysis of sheep, human, and cattle mapping data allowed the construction of a comparative map that confirms and expands the knowledge about evolutionary conservation and break points between the X chromosomes of the three mammalian species.
Assuntos
Cromossomos Humanos X/genética , Mapeamento Físico do Cromossomo , Mapeamento de Híbridos Radioativos/veterinária , Ovinos/genética , Cromossomo X/genética , Animais , Sequência de Bases , Bovinos , Bandeamento Cromossômico , Quebra Cromossômica , Cromossomos Artificiais Bacterianos/genética , Corantes/metabolismo , Simulação por Computador , Sondas de DNA , Fluoresceína-5-Isotiocianato/metabolismo , Corantes Fluorescentes/metabolismo , Marcadores Genéticos/genética , Genoma , Humanos , Hibridização in Situ Fluorescente , Metáfase , Repetições de Microssatélites/genética , Dados de Sequência Molecular , Propídio/metabolismo , Mapeamento de Híbridos Radioativos/métodos , Análise de Sequência de DNA , Especificidade da EspécieRESUMO
The Dlk1-Gtl2 imprinted domain, encompassing the callipyge (CLPG) locus in sheep, has recently been shown to harbor a large number of maternally expressed miRNA genes [1, 2]. Two of these (mir127 and mir136) are processed from a transcript (antiPeg11) that is antisense to Rtl1/Peg11, a paternally expressed intronless gene with homology to the gag and pol polyproteins of Sushi-like retroelements [3]. We herein demonstrate that several additional miRNAs are processed from antiPeg11 and that these regulate Rtl1/Peg11 in trans by guiding RISC-mediated cleavage of its mRNA. This is the first demonstration of miRNA-mediated RNAi involving imprinted genes in mammals.