Imprinting Analysis of RTL1 and DIO3 Genes and Their Association with Carcass Traits in Pigs (Sus scrofa)

Imprinted genes play significant roles in the regulation of fetal growth, development, function of the placenta and postnatal behavior in mammals, but little is known in pigs. In order to investigate the imprinting status of porcine retro-transposon like 1 （RTL1） and type 3 iodothyronine deiodinase （DIO3） genes, DNA or RNA samples of the parents and F1 animals, generated with reciprocal crosses between Large White and Meishan breeds, were isolated, and analyzed by reverse transcription polymerase chain reaction restriction fragment length polymorphism （RT-PCR-RFLP）. The results demonstrated that the RTL1 gene was paternally expressed in 10 tissues, such as the skeletal muscle, heart, spleen, liver, kidney, lung, stomach, fat, small intestine and brain, and D103 gene exhibited paternal expression in the skeletal muscle, heart, spleen, lung, stomach, and brain, in 2-month-old pigs. The association of RTL1 and DI03 with carcass traits was further analyzed in the F2 population of Large White×Meishan pigs. The statistical results showed that the R TL1 A1101G polymorphism （EU781029） was significantly associated with lean meat percentage （LMP） and fat meat percentage （FMP） （P〈0.05）, while the D103 A744C polymorphism （AY533208） was not significantly associated with any carcass traits. These results indicate that the imprinting status of RTL1 and DIO3 is well kept across the mammalian species, and porcine RTL1 may have important roles in muscle growth and fat deposition.

Characterization,Imprinting Status and Tissue Distribution of Porcine GTL2 Gene

The callipyge （CLPG） phenotype, exhibiting polar overdominance （POD）, is an inherited skeletal muscle hypertrophy described in sheep. The callipyge locus maps to the distal portion of ovine chromosome 18 within the DLKI-GTL2 region and corresponds to human chromosome 14 and mouse chromosome 12. The POD phenomenon is confirmed to the homologous region of swine chromosome 7. In order to clone and investigate the expression of porcine GTL2 gene, DNA and RNA samples from 60-day-old F1 animals, generated with reciprocal crosses between Large White and Meishan breeds and their parents, were used. The authors showed that porcine GTL2 acted as a uoncoding RNA. cDNA samples exhibited maternal expression of the gene in the heart, liver, spleen, lung, kidney, stomach, small intestine, skeletal muscle, and fat in pigs, and a unique tissue-specific expression different from that of humans and mice. These results indicated that the gene was conserved in the pig, human, mouse, and bovine. It will be of interest to further study the gene functions in muscle growth and fat deposition.

Tissue Expression Profiles of 5 Putative Imprinted Genes in Bovine Chromosome 29

Genomic imprinting is an epigenetic process that regulates gene expression in the mammalian genome. Although there are specific imprinting differences between the mammalian species, cattle present unique opportunity for characterizing imprinted genes because of its sub-species classification. Five putative imprinted genes (TSSC4, CDKN1C, KCNQ1, PHLDA2 and NAP1L4) on bovine chromosome 29 (Bta 29) which had been characterized to have promoter CGI were quantitatively assayed for their relative expression across eight tissues (muscle, brain, liver, kidney, spinal cord, heart, lymph and skin) sampled in Angus cattle. The differential abundance of these genes in muscle and skin tissues of Angus, White Fulani and N’Dama cattle breeds was comparatively analyzed. These three breeds are representative of the Bos taurus and Bos indicus cattle sub-species while the two tissues are selected based on their strategic economic importance in cattle production. All the genes, except TSSC4, were relatively expressed across all the tissues. It was observed that Angus had the highest differential abundance in muscle tissues for TSSC4, PHLDA2 and NAP1L4 while N’Dama and White Fulani were the most abundant for KCNQ1 and NAP1L4 in skin tissues. The study identified marked differences in the expression profiles of the genes in both muscle and skin tissues of the three breeds that were characteristics of their genetics, environment and nutrition.

前列腺癌印记基因表达的特殊变化一前列腺癌发展和表观遗传调控的预示

Epigenetic dysregulation comprising DNA hypermethylation and hypomethylation, enhancer of zeste homologue 2 （EZH2） overexpression and altered patterns of histone modifications is associated with the progression of prostate cancer. DNA methylation, EZH2 and histone modifications also ensure the parental-specific monoallelic expression of at least 62 imprinted genes. Although it is therefore tempting to speculate that epigenetic dysregulation may extend to imprinted genes, expression changes in cancerous prostates are only well documented for insulin-like growth factor 2 （IGF2）. A literature and database survey on imprinted genes in prostate cancer suggests that the expression of most imprinted genes remains unchanged despite global disturbances in epigenetic mechanisms. Instead, selective genetic and epigenetic changes appear to lead to the inactivation of a sub-network of imprinted genes, which might function in the prostate to limit cell growth induced via the PI3K/Akt pathway, modulate androgen responses and regulate differentiation. Whereas dysregulation of IGF2 may constitute an early change in prostate carcinogenesis, inactivation of this imprinted gene network is rather associated with cancer progression.

Landscape of genomic imprinting and its functions in the mouse mammary gland

Genomic imprinting is an epigenetic modification of DNA,whereby gene expression is restricted to either maternally or paternally inherited alleles.Imprinted genes(IGs)in the placenta and embryo are essential for growth regulation and nutrient supply.However,despite being an important nutrition delivery organ,studies on mammary gland genomic imprinting remain limited.In this study,we found that both the number of IGs and their expression levels decreased during development of the mouse mammary gland.IG expression was lineage-specific and related to mammary gland development and lactation.Meta-analysis of single-cell RNA sequencing data revealed that mammary gland IGs were co-expressed in a network that regulated cell sternness and differentiation,which was confirmed by our functional studies.Accordingly,our data indicated that IGs were essential for the self-renewal of mammary gland stem cells and IG decline was correlated with mammary gland maturity.Taken together,our findings revealed the importance of IGs in a poorly studied nutrition-related organ,i.e.the mammary gland,thus providing a reference for further studies on genomic imprinting.