The hooded phenotype is one of the coat color phenotype seen peculiarly in the rat. The hooded locus showing autosomal recessive inheritance is mapped to chromosome (Chr) 14 and that the hooded phenotype receives modification by hooded-modifier gene showing the linkage to the hooded locus. However, a gene responsible for either the hooded or hooded-modifier gene is not yet identified. To clarify genetic control of hooded phenotype, we carried out genetic linkage studies using BN and LEA rats. For determination of phenotypic variation, we measured ratio of pigmented coat area in parental and their Fsub(1) and Fsub(2) rats. We, then, conducted a genome-wide scan on 152 Fsub(2) rats for linkage with ratio of pigmented coat area for the dorsal, ventral and total regions. A major quantitative trait locus (QTL), D14Got40, showing highly significant linkage contributing 70-90% of the variance for hooded phenotype was detected on Chr 14, which may be correspondent to the hooded locus. In addition, another QTL, D17Rat2, showing highly significant linkage was also detected on Chr 17 in dorsal region phenotype as well as a QTL showing suggestive linkage on Chr15 in ventral region phenotype. We, further, investigated a genome-wide scan for epistatic interactions and detected significant interactions between D14Got40 and D20Mit1, and between D14Got40 and D17Rat2 in the dorsal region phenotype. These results suggest that a major QTL in Chr 14, which is possibly correspondent to the hooded locus, mainly regulates the hooded phenotype with some modifier loci, two of which show epistatic interactions with the hooded locus.

Murine parthenogenetic embryonic stem (ES) cell lines expressing lac zeta reporter gene were isolated after co-transfection with lac zeta reporter gene (pENL) and neoR gene (pSTneo) to TMA-48P cell line of 129/Sv origin. Karyotype analyses showed that all of four transfected cell lines examined contained 41 chromosomes with trisomy 8. Bacterial neoR transgene required for G418 selection were integrated into several chromosomes including chromosome 8. Histological studies of teratomas formed in syngenic mice and embryoid bodies grown in vitro showed that the differentiative potential remained almost identical in chromosomally normal parental cell line and its derivative cell lines trisomic for chromosome 8