ABSTRACT
Nine additional BXD recombinant inbred (RI) strains have been developed from the F2 cross of C57BL/6J and DBA/2J mouse strains. A tenth line stopped breeding in the F12 generation. F20 generation breeding pairs from the nine surviving strains and an F12 pair from the extinct line were genotyped at 319 genetic markers (primarily microsatellites) spanning most of the genome. Where typing data were lacking, the established set of 26 BXD strains also were genotyped at these same loci. The availability of these additional nine strains enhances the value of the BXD RI set for analysis of complex phenotypic traits. The proportion of loci still segregating at the F20 generation was found to closely approximate expectation, suggesting that selection favoring the retention of heterozygosity is not a strong factor. However, the number of crossovers between adjacent markers was frequently less than predicted from consensus map distances. A significant deficiency of recombinants was observed on Chrs 3, 4, 14, and X. On Chr 14, the estimated cumulative BXD map distance between the most proximal and distal markers was only 30.2 cM, compared with a distance of 60.0 cM in the consensus map. On the X Chr, the estimated and predicted cumulative distances were 38.8 and 69.5 cM, respectively. Over all chromosomes, the BXD RI map is 14.5% shorter than predicted from the consensus map. It is suggested that distances in some of the consensus maps are inflated. Alternatively, recombinant genotypes could be selected against during inbreeding owing to allelic interactions affecting fitness. The latter interpretation implies that relatively strong intrachromosomal epistasis is common.
Subject(s)
Mice, Inbred Strains/genetics , Recombination, Genetic , Animals , Chromosome Mapping , Female , Genotype , Male , Mice , Mice, Inbred C57BL , Mice, Inbred DBAABSTRACT
The proteasome plays essential roles in a variety of cellular processes, including degradation of the bulk of cellular proteins, degradation of short-lived proteins such as cell cycle regulators, generation of antigenic peptides, and mediating programmed cell death. One of the best characterized subunits of the 26S proteasome is encoded by the yeast gene SUG1. We report here the cloning and characterization of the Drosophila homolog of this gene, Pros45. At the protein level, Pros45 is highly conserved with respect to its homologs in a variety of taxa: it shows 74% identity to yeast Sug1; 86% to mouse m56/mSug1/FZA-B; 87% to human Trip1; and 97% to moth 18-56. Using a genomic clone as a probe for in situ hyridization to polytene chromesomes, we demonstrated that Pros45 maps to 19F, near the base of the X chromosome. Use of a pros45 cDNA clone as a probe revealed a second site of hybridization at 99CD. Pros45 mRNA is found in the unfertilized egg and in all cells of the early embryo. By the end of embryogenesis, Pros45 is expressed predominantly in the central nervous system. Targeted expression of Pros45 in a variety of different cells using the Gal4 UAS P-element system failed to generate an overt phenotype. This study provides the foundation for further examination of the role of the 26S proteasome in homeostasis and development in Drosophila.
Subject(s)
Carrier Proteins/chemistry , Carrier Proteins/genetics , Drosophila Proteins , Drosophila melanogaster/enzymology , Drosophila melanogaster/genetics , Endopeptidases , Fungal Proteins/genetics , Peptide Hydrolases/chemistry , Peptide Hydrolases/genetics , Proteasome Endopeptidase Complex , Repressor Proteins/genetics , Saccharomyces cerevisiae Proteins , Sequence Homology, Amino Acid , Adenosine Triphosphatases , Amino Acid Sequence , Animals , Base Sequence , Chromosome Mapping , Cloning, Molecular , Drosophila melanogaster/embryology , Gene Expression Regulation, Developmental , Molecular Sequence Data , Saccharomyces cerevisiae , Sequence Analysis, DNA , Sequence Homology, Nucleic AcidABSTRACT
Private duty nursing at home for families with a tracheotomized child is important. Home care nurses can assure that the child is cared for safely and allow the family both training and respite service when it is needed.
