Xu GuiYun

Evaluation of genetic diversity in Chinese indigenous chicken breeds using microsatellite markers.

China is rich in chicken genetic resources, and many indigenous breeds can be found throughout the country. Due to poor productive ability, some of them are threatened by the commercial varieties from domestic and foreign breeding companies. In a large-scale investigation into the current status of Chinese poultry genetic resources, 78 indigenous chicken breeds were surveyed and their blood samples collected. The genomes of these chickens were screened using microsatellite analysis. A total of 2740 individuals were genotyped for 27 microsatellite markers on 13 chromosomes. The number of alleles of the 27 markers ranged from 6 to 51 per locus with a mean of 18.74. Heterozygosity (H) values of the 78 chicken breeds were all more than 0.5. The average H value (0.622) and polymorphism information content (PIC, 0.573) of these breeds suggested that the Chinese indigenous chickens possessed more genetic diversity than that reported in many other countries. The fixation coefficients of subpopulations within the total population (FST) for the 27 loci varied from 0.065 (LEI0166) to 0.209 (MCW0078), with a mean of 0.106. For all detected microsatellite loci, only one (LEI0194) deviated from Hardy-Weinberg equilibrium (HWE) across all the populations. As genetic drift or non-random mating can occur in small populations, breeds kept on conservation farms such as Langshan chicken generally had lower H values, while those kept on large populations within conservation regions possessed higher polymorphisms. The high genetic diversity in Chinese indigenous breeds is in agreement with great phenotypic variation of these breeds. Using Nei’s genetic distance and the Neighbor-Joining method, the indigenous Chinese chickens were classified into six categories that were generally consistent with their geographic distributions. The molecular information of genetic diversity will play an important role in conservation, supervision, and utilization of the chicken resources.

Analysis of SNP markers for chicken blue-shelled gene using PCR-SSCP

The oocyan ( O ) gene determines blue shell pigmentation of domesticated chicken. The O locus is closely linked to ALEV1 on chromosome 1 with a genetic distance of 2.3 cM. Blue eggshells contain a protoporphyrin, biliverdin and zinc biliverdin chelating complex, which belongs to the porphyrin metabolic pathway. A bio-informatic approach was first used to BLAST for the genes of the enzymes in the porphyrin pathway; no gene was detected to specify the O locus. Due to a limited number of simple sequence repeat (SSR) markers around the O locus, polymerase chain reaction–single-strand conformational polymorphism (PCR-SSCP) was then employed to search for candidate single nucleotide polymorphism (SNP) markers. The sequence bearing a marker was found to consist of two transversions at Chr1:61754089T→A and Chr1:61754175A→T, respectively. Population screening showed that 81% of homozygous blue-shelled layers ( OO ) were classified as AA genotype at the SNP loci, while 89% of heterozygous blue-shelled layers ( Oo ) were AB genotype and 93% of tinted layers ( oo ) were BB genotype. The results indicated that there is a close association between O locus and SNP locus, suggesting that the marker locus could be used as a molecular marker in breeding for blue-shelled chickens.

Differentially expressed genes between chicken hybrids and their parents and relationship with heterosis

mRNA differential display was used to analyze the difference of gene expression between cross combinations,EC and CE,and their parental inbreds,White Leghorn(EE)and Silkies(CC)of eight weeks bld.Three genes specified expressed in hybrids and one gene over-expressed in hybrid were found.By cloning,sequencing and BLAST analysis,one specific expression eDNA band was cytosolic isocitrate dehydrogenase gene,the other two were new genes which function were unknown,and the over-expressed eDNA band was proteosome subunit p112 gene.The results implied that functional genes and regulatory genes which specified expressed or over-expressed in chiken hybrids were related to heterosis of some carcass traits.

Whole cDNA sequence cloning and expression of chicken L-FABP gene and its relationship with lipid deposition of hybrid chickens

Liver fatty acid-binding protein (L-FABP) is closely related to intracellular transportation and deposition of lipids. A positive differential displayed fragment was found in the liver tissue among Silkie (CC), CAU-brown chicken (CD), and their reciprocal hybrids (CD and DC) at 8 weeks-old using differential display RT-PCR techniques (DDRT-PCR). Through recycling, sequencing, and alignment analysis, the fragment was identified as chicken liver fatty acid-binding protein gene (L-FABP, GenBank accession number AY321365). Reverse Northern dot blot and semi-quantitative RT-PCR revealed that the avian L-FABP gene was over-expressed in the liver tissue of the reciprocal hybrids (CD and DC) compared to their parental lines (CC and DD), which was consistent with the fact that higher abdomen fat weight and wider inter-muscular fat width observed in the reciprocal hybrids. Considering the higher expression of L-FABP may contribute to the increased lipid deposition in the hybrid chickens, the functional study of avian L-FABP is warranted in future.

Detection of chicken dominant white gene PMEL17 mutation site by a pooling method.

Dominant white locus is one of the major loci affecting feather color in the domestic chicken and its dominant allele I can inhibit the synthesis of the melanin. Therefore, the homozygotes (I/I) or heterozygotes (I/i) show a white phenotype. It has been confirmed that the Dominant white locus encodes PMEL17 protein which is a specific protein and plays a key role in the development of melanocytes, thus PMEL17 gene is identified as a positional candidate gene for the dominant white phenotype in chicken. In our present study, we created an economic and efficient pooling method for detecting PMEL17 mutations in large populations, known as PCR product pooling method, and the steps are as follows: firstly, PMEL17 segments containing the mutation site from individual genomic DNA samples were amplified by PCR; secondly, 10 PCR products were mixed in a pool, and then the pooled PCR samples were separated on non-denatured PAGE gels; and finally, the mutation profile of PMEL17 in certain populations were analyzed. In addition, a comparative study between the genomic DNA pooling and the PCR product pooling method was performed, and the mutation of PMEL17 was also ana-lyzed in our experimental population. In conclusion, the PCR product pooling method proved to be appropriate power to test gene mutations.