Mapping Quantitative Trait Loci Affecting Susceptibility to Marek's Disease Virus in a Backcross Population of Layer Chickens

Abstract

Marek's disease (MD), caused by the oncogenic MD avian herpes virus (MDV), is a major source of economic losses to the poultry industry. A reciprocal backcross (BC) population (total 2052 individuals) was generated by crossing two partially inbred commercial Leghorn layer lines known to differ in MDV resistance, measured as survival time after challenge with a (vv1) MDV. QTL affecting resistance were identified by selective DNA pooling using a panel of 198 microsatellite markers covering two-thirds of the chicken genome. Data for each BC were analyzed separately, and as a combined data set. Markers showing significant association with resistance generally appeared in blocks of two or three, separated by blocks of nonsignificant markers. Defined this way, 15 chromosomal regions (QTLR) affecting MDV resistance, distributed among 10 chromosomes (GGA 1, 2, 3, 4, 5, 7, 8, 9, 15, and Z), were identified. The identified QTLR include one gene and three QTL associated with resistance in previous studies of other lines, and three additional QTL associated with resistance in previous studies of the present lines. These QTL could be used in marker-assisted selection (MAS) programs for MDV resistance and as a platform for high-resolution mapping and positional cloning of the resistance genes.

Genome-Wide Copy Number Variant Analysis in Inbred Chickens Lines With Different Susceptibility to Marek’s Disease

“…It is reported that the QTL for MD resistance and susceptibility were mapped to several chromosomes, including GGA 1-5, 7-9, 15, 18, 26, Z, E21, and E16, by using the backcross or intercross populations (Heifetz et al 2007, 2009; Liu et al 2001; Vallejo et al 1998). To identify whether common genomic variants were detected by using different methods, we compared our CNVs with the QTL regions.…”

“…The MD-related QTL information was downloaded from Chicken QTLdb (http://www.animalgenome.org/cgi-bin/QTLdb/GG/index), which converted the QTL positions from genetic distance (cM) to the physical distance (bp) by using the mapping data from previous research (Heifetz et al 2007, 2009; Liu et al 2001; Vallejo et al 1998). When there is more than 100 bp overlap between CNVs and QTL, we consider that region as shared region.…”

Quantitative trait loci associated with the humoral innate immune response in chickens were confirmed in a cross between Green-Legged Partridgelike and White Leghorn

“…Ghromosomal location of the QTL associated with LPS NA on GGA14 (0-77 cM) overlapped with several QTL associated with LTA NA (Siwek et al, 2006) and KLH specific antibodies (Siwek et al, 2003b(Siwek et al, , 2010. On GGA18, a QTL associated with Marek's disease-related traits (23 cM; Heifetz et al, 2007) was located in close proximity to the vahdated LPS NA QTL (24 cM). Finally, within the GI of the LPS and LTA NA QTL on GGAZ (20-105 cM) an overlap was observed with the QTL associated with antibody response to Brucella abortus (86.8-93 cM; Zhou et al, 2003) and Marek's disease-related traits (0-51.6 cM; Heifetz et al, 2007).…”

“…The QTL linked to LPS and LTA NA on GGA5 (CI: 73-127 cM for LPS QTL and 79-127 cM for LTA QTL) overlapped with the QTL responsible for antibody response to SRBC antigen at 68 cM (Siwek et al, 2003a), cloacal bacterial burden after challenge with Salmonella Enteritidis at 111 cM (Tilquin et al, 2005), cloacal bacterial burden after challenge with Salmonella Typhimurium at 107 cM (Tilquin et al, 2005), time to achieve maximum antibody response to SRBC between 98 and 110 cM (Zhou et al, 2003), and Marek's disease-related traits atl27 cM (Heifetz et al, 2007). On GGA9, within the GI of the LPS NA QTL validated in our study (0-41 cM), a QTL associated with Marek's disease-related traits was mapped (36.3-42.4 cM;Yonash et al, 1999).…”

“…On GGA18, a QTL associated with Marek's disease-related traits (23 cM; Heifetz et al, 2007) was located in close proximity to the vahdated LPS NA QTL (24 cM). Finally, within the GI of the LPS and LTA NA QTL on GGAZ (20-105 cM) an overlap was observed with the QTL associated with antibody response to Brucella abortus (86.8-93 cM; Zhou et al, 2003) and Marek's disease-related traits (0-51.6 cM; Heifetz et al, 2007). Most of the QTL associated with chicken health traits that overlapped the chromosomal location of the QTL reported here were responsible for the adaptive immune response.…”