Gene expression analysis of immune and melanocyte related proteins in Smyth Line (SL) of chickens- The avian model for human autoimmune vitiligo

The Smyth line (SL) of chicken is an excellent animal model for human autoimmune vitiligo. The mechanisms underlying SL chicken vitiligo (SLV) are not clear. However, like in human vitiligo, SLV is a multifactorial disease considered to be caused by complex interactions of genetic, immunologic, metabolic and environmental factors, leading to autoimmune loss of melanocytes in susceptible individuals. The objective of this dissertation research was to dissect the mechanism of SLV expression, making use of the unique opportunity to study the evolving autoimmune lesion before and throughout SLV development in the same individuals. For this study, growing feathers (GF; the melanocyte-containing target-tissue) were collected from SL chickens that never developed SLV (NV) and from SLV chickens at various stages of SLV; i.e., far before and close to SLV onset (BV and EV, respectively), during active (AV) and after complete (CV) SLV. In Chapter II, in situ melanocyte activities in pigmented GF were examined using laser capture microdissection to isolate melanocytes from GF for gene-expression analysis by quantitative (q) RT-PCR. Using this approach, aberrant function of SLV melanocytes was revealed, including increased expression of melanocortin-1 receptor and microphthalm a-associated transcription factor concurrent with decreased expression of tyrosinase-related protein 1 and 2 in BV samples. Additionally, expression of heat shock protein 25 and anti-apoptotic proteins (BCL2 and NR13) was up-regulated in EV and AV samples. In Chapter III, expression of cytokines was determined by qRT-PCR to unravel the functional activity of the immune system in SLV feathers. Cytokines IL-10, IL-21, and IFN-gamma emerged as the signature cytokine profile of active SLV. This finding together with the observed leukocyte infiltration profile provided further support for an important role of Th1-mediated immunity in the autoimmune loss of melanocytes. A microarray study in Chapter IV revealed differentially expressed (DE) genes related to immune activation and melanocyte loss, which were consistent with findings from Chapter II and III. The multifactorial nature of SLV development was also demonstrated by DE genes associated with altered redox reactions and apoptosis. Taken together, both the targeted and global transcriptomic analyses provided valuable information regarding factors leading to SLV development and progression.