Genetic regulation of alcohol dehydrogenase C2 in the mouse. Developmental consequences of the temporal locus (Adh-3t) and positioning of Adh-3 on chromosome 3

Alcohol dehydrogenase isozymes in the mouse: genetic regulation, allelic variation among inbred strains and sex differences of liver and kidney A2 isozyme activity

Genetic analysis of a proposed cis-acting temporal locus (Adh-3t), which regulates alcohol dehydrogenase C2 (ADH-C2) activity in mouse epididymis extracts, among F1 (ddN X BALB/c) X ddN male backcross progeny provided evidence for genetic distinctness between the structural (Adh-3) and temporal (Adh-3t) loci on chromosome 3. Genetic analysis also confirmed the close linkage of Adh-1 (encoding liver and kidney ADH-A2) and Adh-3 (encoding stomach ADH-C2) to within 0.3 centimorgans on the mouse genome. Evidence is presented for a proposed closely linked cis-acting temporal locus (designated Adh-lt) for the A2 isozyme (encoded by Adh-1) controlling the activity of this enzyme in mouse kidney extracts, but having no apparent affect on liver and intestine ADH-A2 activities. An extensive survey of the distribution of Adh-1, Adh-3 and Adh-3t alleles among 65 strains of mice is reported--with the exception of two Japanese strains (ddN and KF), linkage disequilibrium between Adh-3 and Adh-3t was observed. Sex differences in mouse liver and kidney ADH-A2 activities were observed, with male/female ratios of approximately 0.6 and 3 respectively for these tissue extracts.

Gene markers for alcohol-metabolizing enzymes among recombinant inbred strains of mice with differential behavioural responses towards alcohol

The genetic variability of alcohol dehydrogenase (C2 isozyme), aldehyde dehydrogenase (A2 isozyme) and aldehyde oxidase (A2 isozyme) has been examined among recombinant inbred strains of mice which have been previously studied concerning their differential behavioural responses towards alcohol. The results showed no correlation between biochemical phenotype for these loci and behavioural response.

Dorsoventral patterning of the mouse coat by Tbx15

Many members of the animal kingdom display coat or skin color differences along their dorsoventral axis. To determine the mechanisms that control regional differences in pigmentation, we have studied how a classical mouse mutation, droopy ear (de^H), affects dorsoventral skin characteristics, especially those under control of the Agouti gene. Mice carrying the Agouti allele black-and-tan (a^t) normally have a sharp boundary between dorsal black hair and yellow ventral hair; the de^H mutation raises the pigmentation boundary, producing an apparent dorsal-to-ventral transformation. We identify a 216 kb deletion in de^H that removes all but the first exon of the Tbx15 gene, whose embryonic expression in developing mesenchyme correlates with pigmentary and skeletal malformations observed in de^H/de^H animals. Construction of a targeted allele of Tbx15 confirmed that the de^H phenotype was caused by Tbx15 loss of function. Early embryonic expression of Tbx15 in dorsal mesenchyme is complementary to Agouti expression in ventral mesenchyme; in the absence of Tbx15, expression of Agouti in both embryos and postnatal animals is displaced dorsally. Transplantation experiments demonstrate that positional identity of the skin with regard to dorsoventral pigmentation differences is acquired by E12.5, which is shortly after early embryonic expression of Tbx15. Fate-mapping studies show that the dorsoventral pigmentation boundary is not in register with a previously identified dermal cell lineage boundary, but rather with the limb dorsoventral boundary. Embryonic expression of Tbx15 in dorsolateral mesenchyme provides an instructional cue required to establish the future positional identity of dorsal dermis. These findings represent a novel role for T-box gene action in embryonic development, identify a previously unappreciated aspect of dorsoventral patterning that is widely represented in furred mammals, and provide insight into the mechanisms that underlie region-specific differences in body morphology.

Greg Barsh and colleagues show that a member of the well-known family of T-box genes helps to form an important pigmentation boundary in mice

Alcohol dehydrogenases and aldehyde dehydrogenases among inbred strains of mice: multiplicity, development, genetic studies and metabolic roles

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are the major enzymes responsible for the metabolism of alcohols and aldehydes in the body. Both exist as a family of isozymes in mammals, and have been extensively studied in animal models, particularly among inbred strains of mice. Mouse ADH exists as at least three major classes, which are predominantly localized in liver (classes I and III), and in stomach/cornea (class IV). Mouse ALDH exhibits extensive multiplicity, several forms of which have been characterized, including ALDH1 (liver cytoplasmic/class 1 isozyme); ALDH2 (liver mitochondrial/class 2.); ALDH3 (stomach cytosolic/class 3); ALDH4 (liver microsomal/class 3); and ALDH5 (testis cytosolic/class 3). Biochemical, genetic and molecular genetic analyses have been performed on several of these enzymes, including studies on variant forms of ADH and ALDH. Distinct metabolic roles are proposed, based upon their tissue and subcellular distribution characteristics and the biochemical properties for these enzymes.

Molecular analysis of genetic differences among inbred mouse strains controlling tissue expression pattern of alcohol dehydrogenase 4

The ADH gene family in vertebrates is composed of at least seven distinct classes based upon sequence comparisons and enzyme properties. The Adh4 gene product may play an important role in differentiation and development because of its capacity to metabolize retinol to retinoic acid. Allelic gene differences exist among inbred mouse strains which control structure and tissue-specific regulation of Adh4. C57BL/6 mice are unique and have no detectable ADH4 enzyme activity in epididymis and low levels in seminal vesicle, ovary and uterus compared to other strains. C57BL/6 mice express Adh4 in stomach at levels similar to other strains. The goal of this research was to investigate this genetic variation at the molecular level. Northern analysis revealed that the content of ADH4 mRNA in tissues correlate with the enzyme expression pattern. Interestingly, C57BL/6 mice express an ADH4 mRNA in stomach which is smaller than expressed in C3H and other mice. An analysis of the 5'- and 3'-ends of the mRNA using RACE analysis determined that the ADH4 mRNA in C57BL/6 mice is truncated in the 3'-untranslated region. Sequence analysis of RACE products showed that the truncation is due to a single nucleotide mutation which produces an early polyadenylation signal. Additional RACE and Northern analysis revealed that at least five different polyadenylation sites are used in the Adh4 gene. Using 3'-end polymorphisms found between C57BL/6 and C3H strains and RT-PCR, it was shown that the lack of expression in epididymis in C57BL/6 mice is cis-acting in F(1) hybrid animals. The DNA sequence of the proximal promoter (-600/+42 nt) was determined in several mouse strains differing in tissue-specific expression patterns and did not reveal any nucleotide substitutions correlating with expression pattern suggesting further upstream or downstream sequences may be involved.

Genetic regulation of gene-specific mRNA by ethanol in vivo and its possible role in ethanol preference in a cross with RI lines in mice

Relative ethanol preference is a well-recognized phenotype in a number of species, including mice, but the molecular basis for this phenotype remains speculative. We generated novel recombinant inbred (RI) mouse lines from C57BL/6J (ethanol preferring) and BALB/c (ethanol avoiding) strains and evaluated the effect of ethanol feeding on the mRNA levels of three genes (Adh-1, Ahd-2, and Cas-1) of alcohol metabolism. Ethanol feeding affects the mRNA levels of all three genes in both a gene- and a genotype-specific manner. The effect of ethanol feeding on Ahd-2 mRNA, in particular, is highly correlated with the relative ethanol acceptance of the genotypes. DNA sequencing of approximately 500 bp of the 5' upstream region of the Ahd-2 gene has yielded identical sequence for the two strains and the genetically determined associated factors are hypothesized to be regulatory proteins. Quantitative trait locus analysis on the RI lines should lead to the molecular characterization and mapping of such gene-specific regulatory factors.

Studies on the effect of ethanol on dominant lethal mutations in Swiss, C57BL6 and CBA mice

Swiss, C57BL6 and CBA males were given 0.1 ml of 40% ethanol per mouse per day for three consecutive days, intraperitoneally. These males were mated with untreated virgin Swiss females employing a 4-day mating schedule and three consecutive matings were carried out. In another study, C57BL6 males were given an ascending gradient of 5% to 40% ethanol in drinking water for a total period of 11 weeks. These males were mated with C57BL6 females for 2 weeks. Females were dissected at mid-term pregnancy for the examination of uterine contents including total, live and dead implants. All the investigations comprised at least two or three independent experiments which were evaluated independently as well as after pooling the data. Swiss, C57BL6 and CBA males given 0.1 ml of 40% ethanol, intraperitoneally, gave no evidence of any significant increase in post-implantation lethality in the postmeiotic phase of spermatogenesis attributable to ethanol treatment. A moderate but significant reduction in mean total implants indicating pre-implantation losses was seen in Swiss but not in CBA mice. Prolonged feeding of ethanol up to 40% in drinking water failed to provide any evidence of dominant lethal mutations in C57BL6 males at the pre-implantation level and the post-implantation lethals were also not significantly higher than in controls. In Swiss mice, however, the mutagenic index based on both pre- and post-implantation lethality was consistently positive.

Genetics of ocular NAD+-dependent alcohol dehydrogenase and aldehyde dehydrogenase in the mouse: evidence for genetic identity with stomach isozymes and localization of Ahd-4 on chromosome 11 near trembler

Electrophoretic and activity variation of the stomach and ocular isozyme of aldehyde dehydrogenase (designated AHD-4) was observed between C57BL/6J and SWR/J inbred strains of mice. The phenotypes were inherited in a normal mendelian fashion, with two alleles at a single locus (Ahd-4) showing codominant expression. The alleles assorted independently of those at Adh-3 [encoding the stomach and ocular isozyme of alcohol dehydrogenase (ADH-C2)] on chromosome 3. Three chromosome 11 markers, hemoglobin alpha-chain (Hba), trembler (Tr), and rex (Re), were used in backcross analyses which established that Ahd-4 is closely linked to trembler. The distribution patterns for stomach and ocular AHD-4 phenotypes were examined among SWXL recombinant inbred mice, and those for stomach and ocular ADH-C2 among BXD recombinant inbred strains. The data provided evidence for the genetic identity of stomach and ocular ADH-C2 and of stomach and ocular AHD-4.

Molecular analysis of mouse alcohol dehydrogenase: nucleotide sequence of the Adh-1 gene and genetic mapping of a related nucleotide sequence to chromosome 3

The mouse has three genes (Adh) encoding alcohol dehydrogenase (ADH) enzymes of different tissue specificity and catalytic properties. Identified regulatory loci are known to affect the expression of Adh-1 and Adh-3, which are closely linked on chromosome 3. The Adh-1 gene product is expressed predominantly in liver, and its mRNA product is androgen-inducible in kidney. In this study, genomic clones of Adh-1 were obtained from a Balb/cJ DNA library. The nucleotide sequences of all exons, intron/exon boundaries and 5'- and 3'-flanking regions were obtained. The gene spans nearly 13 kb and is divided into nine exons and eight introns. The transcription start point of this gene was determined by S1 nuclease mapping studies and presumptive regulatory regions in the 5'-flanking regions were identified, including a TATA box and a glucocorticoid-responsive element. A restriction fragment length polymorphism in the Adh-1 gene was identified among inbred strains and mapped at the [Adh-1, Adh-3] complex on chromosome 3. An additional 'Adh-like' sequence in the genome was also mapped to chromosome 3 approx. 9 centiMorgans from Adh-1.

Alcohol dehydrogenase isozymes in baboons: tissue distribution, catalytic properties, and variant phenotypes in liver, kidney, stomach, and testis

Isoelectric focusing and cellulose acetate electrophoresis were used to examine the multiplicity, tissue distribution, and variability of alcohol dehydrogenase (ADH) among baboons, a primate species used as a model for research on alcohol metabolism and alcohol-induced liver pathology. Five major ADH isozymes were resolved and distinguished on the basis of their isoelectric points, tissue distributions, relative activities with alcohol substrates, and sensitivities to inhibition with 4-methyl pyrazole. ADH-1 and ADH-2 exhibited class I kinetic properties and were observed in high activity in kidney and liver extracts, respectively. ADH-3 showed class II kinetic properties, exhibiting high activity in stomach extracts, and was widely distributed in extracts of other baboon tissues, including kidney, esophagus, heart, testis, brain, and male sex accessory tissues. ADH-4 also showed class II ADH properties but was found only in liver (similar to human "pi-ADH"). ADH-5 exhibited class III ADH kinetic properties, being inactive with ethanol up to 0.5 M (similar to human "chi-ADH") and was distributed widely in baboon tissue extracts. Major activity variation was observed for liver ADH-4 between different animals. An electrophoretic variant for ADH-3 was observed for the enzyme in stomach, kidney, and testis extracts, and activity variation existed for this isozyme in kidney extracts. It is apparent that baboon ADH shares a number of features with the human ADH phenotype; however, several species-specific differences were observed, particularly for the liver and kidney class I isozymes and for stomach ADH.

Androgen induction of alcohol dehydrogenase in mouse kidney. Studies with a cDNA probe confirmed by nucleotide sequence analysis

A cDNA clone for the beta-chain of human alcohol dehydrogenase (ADH) was used to isolate several cross-hybridizing clones from a mouse liver cDNA library. Clones pADHm9 and a portion of pADHm12 were sequenced. pADHm9 coded for a sequence of 151 C-terminal amino acids and some untranslated sequences from the 3' end of its corresponding mRNA. This clone was identified as an Adh-1 cDNA clone. Consistent with the known expression of Adh-1, this gene was expressed constitutively in liver, whereas the Adh-3 gene product was found only in stomach, lung and reproductive tissues. Furthermore, the translated region of the cDNA shared 91% amino acid sequence homology with rat liver ADH. [32P]pADHm9 was used as a hybridization probe to study the mechanism of androgen induction of kidney ADH activity. Induction of A/J female mice by androgen resulted in a dramatic increase in the steady-state level of Adh-1 mRNA content which correlated with the level of enzyme induction. The size of the mRNA obtained from control or induced kidney and liver tissues was indistinguishable by Northern analysis. [32P]pADHm9 was also used to probe restriction fragments of genomic DNA obtained from several inbred mouse strains. The hybridization patterns, considered with the genetic evidence, suggested that pADHm9 recognized sequences which may be present as only a single copy in the genome. No restriction fragment length polymorphisms were observed among the several inbred mouse strains examined.

Glucosephosphate isomerase (GPI-1) expression in mouse ova: cis regulation of monomer realization

A survey of the glucosephosphate isomerase (GPI-1) activity expressed in mature mouse ova has revealed multiple interstrain differences. Genetic variation at a site either linked to (less than 1.1 cM) or directly associated with Gpi-1 affects the realization of GPI-1 monomers during the later stages of oocyte maturation.

Genetic considerations in the effects of ethanol in mice. II. A trans-acting inducibility regulator(s) affecting alcohol dehydrogenase (ADH) activity

The inducibility of alcohol dehydrogenase (ADH) has been recognized in different systems including maize, Drosophila, and mice. Our earlier results showed strain-specific ADH responses to chronic ethanol administration relative to matched littermate controls in mice. For this study we used two strains which showed "induction" (BALB/c and S.W.) and two strains which showed "repression" (C57BL/6J and 129/ReJ) to produce three sets of F1 hybrids and their reciprocals and one set (BALB/c X C57BL/6J) of recombinant inbred (RI) lines. The ADH properties of the resulting genotypes were again evaluated following 15% ethanol treatment in drinking water (2 weeks) in relation to their littermate matched controls in replicated trials. Our F1 results suggest complete dominance for induction over repression at the phenotypic level, and the two repressed strains showed complementation. No significant differences were observed in the reciprocal F1's and all pairs of a given genotype-treatment combination yielded consistent results. The 1:1 segregation of RI lines suggests a single gene difference for ADH inducibility between BALB/c and C57BL/6J. These findings suggest the presence of a trans-acting inducibility regulator(s) for ADH which may or may not represent a single locus. Variability for such regulatory elements may provide an explanation for the commonly observed individual differences in natural populations for response to alcohol including alcohol metabolism.

Alcohol dehydrogenase in the mouse epididymis. Genetic variation and cellular localization

The cellular localization of alcohol dehydrogenase (ADH) in the mouse epididymis was investigated using differential substrate specificities and genetic variation as a means of distinguishing these enzymes histochemically in tissue sections. ADH-C2 exhibited high activity in BALB/c epididymis and was observed as a discrete zone within duct epithelial cells near the nuclei. This isozyme exhibited no detectable activity in C57BL/6J epididymis extracts or histochemical sections.

Biochemical genetics of aldehyde reductase in the mouse: Ahr-1--a new locus linked to the alcohol dehydrogenase gene complex on chromosome 3

Electrophoretic and activity variants for a liver aldehyde reductase (AHR-A2) among strains of Mus musculus have been used in genetic analyses to demonstrate close linkage between the locus encoding this enzyme (designated Ahr-1) and the alcohol dehydrogenase gene complex on chromosome 3. No recombinants were observed between Adh-3 (encoding alcohol dehydrogenase C2; ADH-C2) and Ahr-1 among 42 backcross animals. Moreover, linkage disequilibrium between these loci was observed among 58 of 60 strains of mice examined and among seven recombinant inbred strains derived from C57BL/6J and BALB/c mice. Liver hexonate dehydrogenase (HDH-A) was electrophoretically invariant among the strains examined. Gel filtration analyses demonstrated that AHR-A2 and HDH-A had native molecular weights of approximately 80,000 and 32,000, respectively. Three-banded allozyme patterns for AHR-A2 in CBA/H x castaneus hybrid animals were consistent with a dimeric subunit structure. Comparative substrate and coenzyme specificities for AHR-A2, HDH-A, and ADH-A2 (liver ADH isozyme) were examined. AHR-A2 exhibited a defined specificity toward p-nitrobenzaldehyde as substrate, whereas the other enzymes exhibited broad specificities toward various aliphatic, aromatic, and monosaccharide aldehydes. It is proposed that Ahr-1 is a product of a gene duplication event during mammalian evolution of the primordial mammalian Adh locus and that considerable divergence in catalytic properties has subsequently occurred.

Mouse alcohol dehydrogenase isozymes: products of closely localized duplicate genes exhibiting divergent kinetic properties

Electrophoretic variants for the stomach isozyme (ADH-C2) and liver isozyme (ADH-A2) of alcohol dehydrogenase in strains of Mus musculus have been used in genetic analyses to demonstrate close linkage between the structural genes (Ahd-3 and Adh-1, respectively) encoding these enzymes. No recombinants were observed between these loci among 126 backcross animals, which places them less than 0.8 centimorgans apart. Previous studies have positioned Adh-3, and a temporal locus (ADh-3t), on chromosome 3 (Holmes, "79; Holmes et al., "80). Kinetic analyses on partially purified preparations of these isozymes have demonstrated widely divergent catalytic properties and inhibitor specificities. The liver isozyme exhibited Michaelis constants that were nearly 3 orders of magnitude lower than the stomach isozyme for various alcohol and aldehyde substrates. Moreover, aminopropyl pyrazole strongly inhibited ADH-A2 (Ki=1.2M), whereas ADH-C2 was insensitive to inhibition under the conditions used. It is proposed that Adh-1 and Adh-3 are products of a recent gene duplication event during mammalian evolution and that considerable divergence in the active sites of these enzymes and the "temporal" genes controlling loci expression in differentiated tissues has subsequently occurred.