[Investigation of pseudoautosomal and bordering regions in avian Z and W chromosomes with the use of large insert genomic BAC clones].

To study pseudoautosomal and bordering regions in the avian Z and W chromosomes, we used seven BAC clones from genomic libraries as DNA probes of fragments of different gametologs of the ATP5A1 gene located close to the proximal border of the pseudoautosomal region (PAR) of sex chromosomes of domestic chicken and Japanese quail. Localization of BAC clones TAM31-b100C09, TAM31-b99N01, TAM31-b27P16, and TAM31-b95L18 in the short arm of Z chromosomes of domestic chicken and Japanese quail (region Zp23-p22) and localization of the BAC clones CHORI-261-CH46G16, CHORI-261-CH33F10, and CHORI-261-CH64F22 on W chromosomes of these species and in the short arm of Z chromosomes (region Zp23-p22) were determined by fluorescence in situ hybridization with the use of W-specific probes. The difference in the localization of the BAC clones on the Z and W chromosomes is probably explained by divergence of the nucleotide sequences of different sex chromosomes located beyond the pseudoautosomal region.

Expression of positional candidates for shell thickness in the chicken.

Expression of 12 positional candidates for QTL affecting shell thickness at 53 wk of lay age (ST53) was investigated by real-time PCR in the distal part of chicken oviducts (uterus) with a forming eggshell. In the local chicken breed Green-legged Partridgenous, the complete cDNA CR523443 (ChEST985k21) was downregulated with ratio of means 0.49 (P < or = 0.01) in the group with low ST53 (248.6 +/- 16.62 microm) relative to the group with the highest ST53 (372.4 +/- 2.07 microm). Expression of this gene was highly correlated (0.85, P < or = 0.01) with shell thickness. No significant difference in expression between the 2 groups with thick (378.4 +/- 3.65 microm) and thin (227.8 +/- 8.99 microm) shell and no significant correlation of expression level with ST53 were detected in Rhode Island Red, which could be explained by strict selection to egg quality traits, including optimal shell thickness in this commercial layer breed. These data suggested that CR523443 was a candidate gene for QTL ST53 in the chicken.

Chromosomal localization of seven HSA3q13-->q23 NotI linking clones on chicken microchromosomes: orthology of GGA14 and GGA15 to a gene-rich region of HSA3.

Double-color fluorescence in situ hybridization was performed on chicken chromosomes using seven unique clones from the human chromosome 3-specific NotI linking libraries. Six of them (NL1-097, NL2-092, NL2-230, NLM-007, NLM-118, and NLM-196) were located on the same chicken microchromosome and NL1-290 on another. Two chicken microchromosome GGA15-specific BAC clones, JE024F14 containing the IGVPS gene and JE020G17 containing the ALDH1A1 gene, were cytogenetically mapped to the same microchromosome that carried the six NotI linking clones, allowing identification of this chromosome as GGA15. Two GGA14-specific clones, JE027C23 and JE014E08 containing the HBA gene cluster, were co-localized on the same microchromosome as NL1-290, suggesting that this chromosome was GGA14. The results indicated that the human chromosomal region HSA3q13-->q23 is likely to be orthologous to GGA15 and GGA14. The breakpoint of evolutionary conservation of human and chicken chromosomes was detected on HSA3q13.3-->q23 between NL1-290, on the one hand, and six other NotI clones, on the other hand. Considering the available chicken-human comparative mapping data, another breakpoint appears to exist between the above NotI loci and four other genes, TFRC, EIF4A2, SKIL and DHX36 located on HSA3q24-->qter and GGA9. Based on human sequences within the NotI clones, localization of the six new chicken coding sequences orthologous to the human/rodent genes was suggested to be on GGA15 and one on GGA14. Microchromosomal location of seven NotI clones from the HSA3q21 T-band region can be considered as evidence in support of our hypothesis about the functional analogy of mammalian T-bands and avian microchromosomes.