F. Abel Ponce de Leon

Chicken genome mapping: a new era in avian genetics

More than 460 loci representing either expressed or anonymous sequences have been mapped on to the first comprehensive molecular genetic linkage map of the chicken genome. Here, we review the current status of poultry genome mapping and discuss some of the new opportunities this provides.

A New Method for Detecting Nucleolus Organizer Regions in Fish Chromosomes Using Denaturation and Propidium Iodide Staining

A rapid method for detecting nucleolus organizer regions (NORs) in fish chromosomes based on thermal denaturation and staining with propidium iodide is described. Under epifluorescence, the NORs of 15 fish species from six families could be detected. This protocol differentiates constitutive heterochromatin in mammalian and avian chromosomes, and in some cases, heterochromatic blocks in fish chromosomes. The staining of NORs of fish chromosomes with propidium iodide following denaturation with formalin is likely the result of differential denaturation of the rDNA due to the thermal characteristics of AT- and GC-rich domains of the rDNA cistron. This technique provides a new useful marker for descriptive fish cytogenetic studies.

Analysis of the Effect of Endogenous Viral Genes in the Smyth Line Chicken Model for Autoimmune Vitiligo

The Smyth line (SL) chicken, an animal model for autoimmune human vitiligo, is characterized by a spontaneous posthatch pigment loss, determined to be the result of an autoimmune phenomenon. Because endogenous virus (EV) genes have been reported to be associated with a number of autoimmune diseases of human and animal models, we designed this experiment to investigate the role of EV in the SL vitiligo by using the complete sequence of Rous-associated virus-2 as a probe for EV. An F(2) resource population was developed by the matings of SL and parental control (BL) chickens. Linkage disequilibrium between vitiligo and EV was apparent (16.2-kb SacI fragment, P </= 0.05 and a 19-kb HindIII fragment, P </= 0.03). Methylation analyses revealed that the EV and endogenous avian retroviral (EAV) genes were methylated in both the SL and BL sublines of chickens; therefore, methylation does not appear to be responsible for the differences in the expression of vitiligo between SL and BL sublines. Expression of the EV genes correlated with the disease in vitiliginous SL101 birds and also in 5-Azacytidine-induced vitiliginous BL101 parental control chickens. Only one EV locus was detected in the unrelated Light Brown Leghorn control chickens (1q14) by in situ hybridization, whereas 3 EV loci were identified in SL101 and BL101 chickens (1p25, 2q26, and an unidentifiable microchromosome). Our observations indicate that EV genes may play a role in the induction of autoimmune vitiligo in the SL chicken model.