Gavin Kelsey

Characterization of the mouse HNF-4 gene and its expression during mouse embryogenesis

Hepatocyte nuclear factor 4 (HNF-4) is a member of the nuclear receptor gene superfamily with unknown ligand. It has been assumed to play an important role in the regulation of gene expression in the liver. Here, we report the cloning and characterization of the mouse HNF-4 gene, as well as its expression during embryogenesis. The HNF-4 protein is encoded by ten exons. The gene structure is unique in the steroid receptor superfamily in that the second zinc finger is encoded by two exons. HNF-4 mRNA is expressed in a limited number of mouse adult tissues: liver, kidney, intestine, stomach and skin. HNF-4 could play an important role in the formation and function of visceral yolk sac and in the development of the liver and kidney since its mRNA, as determined by in situ hybridization, appears upon primary differentiation of these organs. As a first step in the study of the regulatory elements of the HNF-4 gene, we mapped the transcription start site and carried out DNase I hypersensitive site (HS) analysis over a region of approximately 22kb upstream of the gene. The complexity of the HSs suggests that multiple elements might contribute to the transcriptional regulation of the HNF-4 gene.

Mouse chromosome 7

Center for Neuroscience, University of Tennessee, Memphis, 855 Monroe Avenue, Memphis, Tennessee 38163, USA Department of Carcinogenesis, University of Texas Science Park, Research Division, Smithville, Texas 78957, USA Department of Biochemistry and Cell Biology, SUNY at Stony Brook, Stony Brook, New York 11794-5215, USA Division of Genetics, Children’s Hospital of Philadelphia, 34th and Civic Center Boulevard, Philadelphia, Pennsylvania 19104, USA Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, Pennsylvania 19111, USA

Molecular mapping of albino deletions associated with early embryonic lethality in the mouse

The albino-deletion complex consists of more than 37 deletions that remove an area of mouse chromosome 7 including the albino coat-color locus. Previous genetic and embryological studies with five of these deletions (C11DSD, c5FR60Hg, c4FR60Hd, c2YPSj, c6H) defined at least two genes required for normal development of the embryonic and extraembryonic ectoderm of early postimplantation embryos. A molecular genetic analysis of this region has been initiated using palb18, a genomic clone that defines the D7TM18 locus that maps to a region of chromosome 7 removed by the c11DSD deletion but not by the c5FR60Hg, c4FR60Hd, c2YPSj, or c6H deletions. palb18 was obtained by chromosomal microdissection and microcloning of the wild-type albino region. A genomic clone isolated with palb18 contains a repeat sequence localized primarily to the proximal region of the five deletions. The repeat sequence hybridizes differentially to the five deletion DNAs. The patterns of hybridization associated with these DNAs were used to define the order of the proximal breakpoints as centromere-c11DSD-c2YPSj-(c5FR60Hg-c4FR60Hd)- c6H. This order was confirmed by isolation of additional single-copy sequences. The molecular probes described here should allow for identification and isolation of the deletion breakpoints and thus provide immediate access to the distal side of the deletions where the genes affecting the development of the embryonic and extraembryonic ectoderm are located.

Physical mapping of the albino-deletion complex in the mouse to localize alf/hsdr-1, a locus required for neonatal survival

The albino-deletion complex in the mouse defines a genetically well-characterized region of chromosome 7 in which a number of loci essential for normal development and viability reside. One locus, designated alf or hsdr-1, is necessary for neonatal survival. Its absence results in hypoglycemia associated with biochemical and ultrastructural abnormalities in hepatocytes and proximal tubule cells of the kidney. We constructed a long-range physical map of the region defined by the proximal segment of the albino-deletion complex as a step toward localizing alf/hsdr-1. Sixteen markers, including 11 whose isolation is described here and in the accompanying paper (A. Schedl et al., 1992, Genomics 14, 288-297), were ordered on a panel of albino-deletion DNAs and their distribution was examined by pulsed-field gel electrophoresis. The resulting approximately 4300-kb physical map covers the entire region absent from the prototypic alf/hsdr-1 deletion c14CoS, estimated as approximately 3600 kb. Since the deletion c11DSD complements and overlaps most of c14CoS, alf/hsdr-1 was mapped at the proximal extreme of c14CoS, approximately 3000 kb from the albino locus. The density of CpG islands was found to be very heterogeneous across the region mapped.

Germ line transmission of yeast artificial chromosomes in transgenic mice

Several groups have recently reported the successful generation of transgenic mice harbouring yeast artificial chromosomes (YACs). Different methodological approaches have been shown to produce similar results, namely, the faithful expression of the transgenes carried on YAC DNA. In this paper, we compare the reported techniques for obtaining transgenic mice carrying YACs using a 250-kb YAC bearing the mouse tyrosinase gene. These methods include: microinjection of gel-purified YAC DNA into pronuclei of fertilized mouse oocytes, yeast spheroblast fusion with embryonic stem (ES) cells and lipofection of YAC DNA into ES cells. Taken together, these reports show that the delivery of large genomic regions covering a gene of interest (such as those cloned in YAC vectors) is feasible, and will ensure appropriate temporal and spatial expression of the transgene at a level comparable to that of the endogenous counterpart.

Chromosome jumping from flanking markers defines the minimal region for alf/hsdr-1 within the albino-deletion complex

The locus alf/hsdr-1, defined by the albino-deletion complex on mouse chromosome 7, is essential for neonatal survival. Animals homozygous for a subset of the deletions die shortly after birth due to impaired gene expression in liver parenchymal cells and kidney proximal tubular cells. Here, we describe a detailed analysis of the region containing alf/hsdr-1 by means of chromosome jumping from flanking markers. Three chromosome jumping libraries based on the restriction enzymes XmaI and SalI were constructed. Isolation of eight jumping clones distributed over 450 kb allowed more than 240 kb to be cloned in genomic lambda and cosmid libraries. Five of the probes map within the minimal genetic interval for alf/hsdr-1, which is defined by the proximal borders of the deletions c10R75M and c11DSD. The breakpoints of these deletions were precisely mapped, which allowed alf/hsdr-1 to be localized to a 310-kb interval.

Lessons from lethal albino mice.

Results from the analysis of mice homozygous for lethal albino deletions suggested the existence of a locus involved in the regulation of gene expression in the liver. The surprising finding that the locus encodes an enzyme active in tyrosine metabolism forces us to re-evaluate the lethal albino phenotype and advises caution in the interpretation of seemingly simple phenotypes.

Multiple effects on liver-specific gene expression in albino lethal mice caused by deficiency of an enzyme in tyrosine metabolism

Summary alf/hsdr-1 is a locus in the mouse defined by albino deletions to be essential for neonatal viability. Homozygous deletion of alf/hsdr-1 leads to a pleiotropic phenotype in liver and kidney, including impaired perinatal activation of hormone-dependent genes, and the induction of detoxifying enzymes and early-response genes. To elucidate the molecular basis of this complex phenotype, we have identified the gene mapping at alf/hsdr-1 by positional cloning, using overlapping albino locus deletions to define the location of alf/hsdr-1. The gene encodes fumarylacetoacetate hydrolase, FAH, an enzyme of tyrosine metabolism. Genetically determined FAH deficiency in man leads to a severe liver failure in infants. In mice, we find that the normal sites of expression of FAH correlate tightly with cell-types which display abnormalities in albino lethal mice. The identification of the Fah gene as a candidate for alf/hsdr-1 offers a novel explanation for the complex phenotype, one into which all aspects can be accommodated. The phenotype can now be understood as a sequence of responses to toxic electrophilic metabolites.

The Albino Perinatal Lethal Mutation: Identification of Affected mRNAs and Mapping of the Locus by Pulsed-Field Gel Electrophoresis

The analysis of chromosomal deletions overlapping at the albino locus in the mouse has led to the postulation of a number of loci in this region essential for viability. One of these, the perinatal survival locus, is thought to be important for the differentiation of the liver since its deletion results in the deficiency of a set of liver-specific enzymes and ultrastructural abnormalities in the hepatocyte. By differential cDNA screening we have isolated and examined the expression of a panel of mRNAs influenced by deletion of the locus. This has been done in an attempt to elucidate the role of the normal gene product. In addition, as a prelude to cloning the perinatal survival locus, a long-range restriction map has been established onto which the extents of albino locus deletions are being placed.