The structural gene for F liver protein (Flp) maps to chromosome 5 of the mouse

The gamma phosphorylase kinase gene, Phkg, maps to mouse chromosome 5 near Gus

Phosphorylase kinase is a multimeric regulatory enzyme in the glycogenolytic pathway. Interest in various types of phosphorylase kinase enzyme deficiency has focused attention on cloning and mapping the enzyme subunits. We report the mapping of the catalytic gamma subunit gene, Phkg, to mouse Chromosome (Chr) 5 near beta-glucuronidase (Gus), between alpha fetoprotein (Afp) and erythropoietin (Epo). In addition, PCR-based polymorphism assays have been developed for the human (EPO) and mouse erythropoietin genes, and a unique recombinant inbred strain distribution pattern has been defined for Epo, a distal anchor marker on mouse Chr 5.

Characterization of murine middle repetitive DNA

We have characterized four sequences from a small library containing a subset of the repetitive families of the mouse. Each clone has a repetition frequency of less than 1,100 copies per genome and each clone represents a unique family of middle repetitive DNA. One clone (pMR111) shares homology with mouse intracisternal A-particle (IAP) elements, a second clone (pMR89) has partial homology with a sequence in the 3' untranslated region of the human fibulin gene, while two clones (pMR6, pMR66) are new that have no homology to any reported DNA sequence. Each clone hybridizes to one or two discrete RNA transcripts from one or more tissues of the mouse. Clone pMR66 detected restriction fragment length polymorphisms (RFLPs) at three loci in genomic mouse DNA, defining loci at the distal end of chromosome 5 and the proximal end of chromosome 7. The third locus is unmapped. This study demonstrates that cloned repeats from a repetitive DNA library are a potential source of genetic markers.

Molecular cloning, functional expression, and chromosomal localization of mouse hepatocyte nuclear factor 1

The homeodomain-containing transcription factor hepatocyte nuclear factor 1 (HNF-1) most likely plays an essential role during liver organogenesis by transactivating a family of greater than 15 predominantly hepatic genes. We have isolated cDNA clones encoding mouse HNF-1 and expressed them in monkey COS cells and in the human T-cell line Jurkat, producing HNF-1 DNA-binding activity as well as transactivation of reporter constructs containing multimerized HNF-1 binding sites. In addition, the HNF-1 gene was assigned by somatic cell hybrids and recombinant inbred strain mapping to mouse chromosome 5 near Bcd-1 and to human chromosome 12 region q22-qter, revealing a homologous chromosome region in these two species. The presence of HNF-1 mRNA in multiple endodermal tissues (liver, stomach, intestine) suggests that HNF-1 may constitute an early marker for endodermal, rather than hepatocyte, differentiation. Further, that HNF-1 DNA-binding and transcriptional activity can be conferred by transfecting the HNF-1 cDNA into several cell lines indicates that it is sufficient to activate transcription in the context of ubiquitously expressed factors.

The organ distribution of F protein in the mouse

F protein is of unknown function and found principally in the liver, with smaller amounts detectable by gel diffusion and immunostaining in kidney and brain. By taking advantage of a newly developed radioimmunoassay, capable of detecting down to 1 ng ml-1 of F protein, the organ distribution of this molecule in the mouse was re-examined. F protein was not confined to the previously known tissues and indeed was detected at different levels in every organ studied. The highest concentration (6-10 mg g-1 wet tissue) was found in the liver, but significant amounts (2-25 micrograms g-1) were also found in kidney, heart, and brain. Lower quantities were detectable in all other tissues studied. The presence of F protein in the thymus, and the lack of tolerance to this in bone marrow chimaeras between mice of different F protein types, places certain constraints on the amount and/or location of a protein required for tolerization.