Evolutionary amplification of a pseudogene

Major urinary proteins, alpha(2U)-globulins and aphrodisin

The major urinary proteins (MUPs) are proteins secreted by the liver and filtered by the kidneys into the urine of adult male mice and rats, the MUPs of rats being also referred to as alpha(2U)-globulins. The MUP family also comprises closely related proteins excreted by exocrine glands of rodents, independently of their sex. The MUP family is an expression of a multi-gene family. There is complex hormonal and tissue-specific regulation of MUP gene expression. The multi-gene family and its outflow are characterized by a polymorphism which extends over species, strains, sexes, and individuals. There is evidence of evolutionary conservation of the genes and their outflow within the species and evidence of change between species. MUPs share the eight-stranded beta-barrel structure lining a hydrophobic pocket, common to lipocalins. There is also a high degree of structural conservation between mouse and rat MUPs. MUPs bind small natural odorant molecules in the hydrophobic pocket with medium affinity in the 10(4)-10(5) M(-1) range, and are excreted in the field, with bound odorants. The odorants are then released slowly in air giving a long lasting olfactory trace to the spot. MUPs seem to play complex roles in chemosensory signalling among rodents, functioning as odorant carriers as well as proteins that prime endocrine reactions in female conspecifics. Aphrodisin is a lipocalin, found in hamster vaginal discharge, which stimulates male copulatory behaviour. Aphrodisin does not seem to bind odorants and no polymorphism has been shown. Both MUPs and aphrodisin stimulate the vomeronasal organ of conspecifics.

Intraspecific evolution of a gene family coding for urinary proteins

The genome of the laboratory mouse contains about 35 major urinary protein (MUP) genes, many of which are clustered on chromosome 4. We have used distance and parsimony methods to estimate phylogenetic relationships between MUP genes from nucleotide sequence and restriction maps. By analyzing coding sequences we show that the genes fall into four main groups of related sequences (groups 1-4). Comparisons of restriction maps and the nucleotide sequences of hypervariable regions that lie 50 nucleotides 5' to the cap sites show that the group 1 genes and probably also the group 2 pseudogenes fall into subgroups. The most parsimonious trees are consistent with the evolution of the array of group 1 and 2 genes by mutation accompanied by a process tending toward homogenization such as unequal crossing-over or gene conversion. The phylogenetic grouping correlates with grouping according to aspects of function. The genomes of the inbred strains BALB/c and C57BL contain different MUP gene arrays that we take to be samples from the wild population of arrays.

Differential expression in male and female mouse liver of very similar mRNAs specified by two group 1 major urinary protein genes

The major urinary proteins of the mouse are encoded by a large multigene family composed of several distinct groups of genes distinguished by differences in sequence and expression characteristics. The genes in the largest group (group 1) show greater than 99% pairwise similarity in their exons. By hybridization between RNA and a specifically designed oligonucleotide, we confirmed that genes of this group are expressed mainly in the liver. By using additional gene-specific oligonucleotide probes, we have been able to distinguish between the species of mRNA corresponding to two of these genes and to measure their abundance in male and female liver. Both mRNAs are present in male liver at high but different levels. Both are also present in female liver, one at a much lower level than in the male and the second at a very low level indeed. Both are present at male levels in the livers of females induced with testosterone. These results show unequivocally that the expression of different group 1 Mup genes is differentially influenced by the hormonal status of the mouse.

Differential expression in male and female mouse liver of very similar mRNAs specified by two group 1 major urinary protein genes

The major urinary proteins of the mouse are encoded by a large multigene family composed of several distinct groups of genes distinguished by differences in sequence and expression characteristics. The genes in the largest group (group 1) show greater than 99% pairwise similarity in their exons. By hybridization between RNA and a specifically designed oligonucleotide, we confirmed that genes of this group are expressed mainly in the liver. By using additional gene-specific oligonucleotide probes, we have been able to distinguish between the species of mRNA corresponding to two of these genes and to measure their abundance in male and female liver. Both mRNAs are present in male liver at high but different levels. Both are also present in female liver, one at a much lower level than in the male and the second at a very low level indeed. Both are present at male levels in the livers of females induced with testosterone. These results show unequivocally that the expression of different group 1 Mup genes is differentially influenced by the hormonal status of the mouse.

Concerted gene duplications in the two keratin gene families

Evolutionary trees were derived from the keratin protein sequences using the Phylogeny Analysis Using Parsimony (PAUP) set of programs. Three major unexpected conclusions were derived from the analysis: The smallest keratin protein subunit, K#19 (Moll et al. 1982), is not the most primitive one, but has evolved to fulfill a highly specialized function, presumably to redress the unbalanced synthesis of keratin subunits. Second, the ancestors of keratins expressed in the early embryonic stages, K#8 and K#18, were the first to diverge from the ancestors of all the other keratins. The branches leading to these two keratins are relatively short, indicating a comparatively strong selection against changes in the sequences of these two proteins. Third, the two keratin families show extraordinary parallelism in their patterns of gene duplications. In both families the genes expressed in embryos diverged first, later bursts of gene duplications created the subfamilies expressed in various differentiated cells, and relatively recent gene duplications gave rise to the hair keratin genes and separated the basal cell-specific keratin from those expressed under hyperproliferative conditions. The parallelism of gene duplications in the two keratin gene families implies a mechanism in which duplications in one family influence duplication events in the other family.

Time for acquiring a new gene by duplication

In view of the widespread occurrence of gene families in eukaryotic genomes that suggests the importance of gene duplication in evolution, a population genetic model incorporating unequal crossing-over was formulated. By using this model, the time needed for acquiring a new gene is investigated by an approximate analytical method and by computer simulations. The model assumes that natural selection favors those chromosomes with more beneficial genes than other chromosomes in the population, as well as random genetic drift, mutation, and unequal crossing-over. Starting from a single gene copy, it is found that the time for acquiring another gene with a new function is dependent on the rates of occurrence of unequal crossing-over and mutation. Within a realistic range of parameter values, the required time was at least several times 4N generations, where N is the effective population size. Interchromosomal unequal crossing-over at meiosis is more effective than intrachromosomal (between sister chromatids) unequal crossing-over for obtaining a new gene, provided that other parameters are the same. However, the genetic load for acquiring a gene is larger under the model of interchromosomal crossing-over. The relevance of this finding to the advantage of sexual reproduction is discussed.

Identification and characterization of functional genes encoding the mouse major urinary proteins

Mouse Ltk- cells were stably transfected with cloned genes encoding the mouse major urinary proteins (MUPs). C57BL/6J MUP genomic clones encoding MUP 2 (BL6-25 and BL6-51), MUP 3 (BL6-11 and BL6-3), and MUP 4 (BL6-42) have been identified. In C57BL/6J mice, MUP 2 and MUP 4 are known to be synthesized in male, but not female, liver, and MUP 3 is known to be synthesized in both male and female liver and mammary gland. A BALB/c genomic clone (BJ-31) was shown to encode a MUP that is slightly more basic than MUP 2 and was previously shown to be synthesized in both male and female liver of BALB/c but not C57BL/6 mice. Comigration on two-dimensional polyacrylamide gels of the MUPs encoded by the transfecting gene provides a basis for tentative identification of the tissue specificity and mode of regulation of each gene. DNA sequence analysis of the 5' flanking region indicates that the different MUP genes are highly homologous (0.20 to 2.40% divergence) within the 879 base pairs analyzed. The most prominent differences in sequence occur within an A-rich region just 5' of the TATA box. This region (from -47 to -93) contains primarily A or C(A)N nucleotides and varies from 15 to 46 nucleotides in length in the different clones.

Identification and characterization of functional genes encoding the mouse major urinary proteins

Mouse Ltk- cells were stably transfected with cloned genes encoding the mouse major urinary proteins (MUPs). C57BL/6J MUP genomic clones encoding MUP 2 (BL6-25 and BL6-51), MUP 3 (BL6-11 and BL6-3), and MUP 4 (BL6-42) have been identified. In C57BL/6J mice, MUP 2 and MUP 4 are known to be synthesized in male, but not female, liver, and MUP 3 is known to be synthesized in both male and female liver and mammary gland. A BALB/c genomic clone (BJ-31) was shown to encode a MUP that is slightly more basic than MUP 2 and was previously shown to be synthesized in both male and female liver of BALB/c but not C57BL/6 mice. Comigration on two-dimensional polyacrylamide gels of the MUPs encoded by the transfecting gene provides a basis for tentative identification of the tissue specificity and mode of regulation of each gene. DNA sequence analysis of the 5' flanking region indicates that the different MUP genes are highly homologous (0.20 to 2.40% divergence) within the 879 base pairs analyzed. The most prominent differences in sequence occur within an A-rich region just 5' of the TATA box. This region (from -47 to -93) contains primarily A or C(A)N nucleotides and varies from 15 to 46 nucleotides in length in the different clones.

Nucleotide sequences of liver, lachrymal, and submaxillary gland mouse major urinary protein mRNAs: mosaic structure and construction of panels of gene-specific synthetic oligonucleotide probes

The mouse major urinary proteins (MUPs) are encoded by a gene family of about 35 to 40 members. MUPs are synthesized in at least six secretory tissues under a variety of developmental and endocrine controls, but the identities of the individual genes expressed in each tissue have not previously been established. In this article, we present the nucleotide sequences of five MUP mRNAs which we designate MUP I through V. MUPs I, II, and III are the most abundant MUP mRNA species in the liver, and MUPs IV and V are the most abundant MUP mRNA species in the lachrymal gland and the submaxillary gland, respectively. The sequence data show that each of the five mRNAs is encoded by a distinct member of the gene family. The structures of the MUP mRNA consist of interspersed segments of variable and conserved sequences. On the basis of the sequences of the variable segments, gene-specific panels of synthetic oligonucleotide probes were prepared. The gene-specific panels were used to identify cloned genes and, as described in the accompanying paper (K. Shahan, M. Denaro, M. Gilmartin, Y. Shi, and E. Derman, Mol. Cell. Biol. 7:1947-1954, 1987), to characterize the expression of MUP genes I through V.

Expression of six mouse major urinary protein genes in the mammary, parotid, sublingual, submaxillary, and lachrymal glands and in the liver

Mouse major urinary proteins (MUPs) are encoded by a family of about 35 to 40 highly conserved genes. In the preceding paper (K. Shahan, M. Gilmartin, and E. Derman, Mol. Cell. Biol. 7:1938-1946, 1987), we presented the sequences of the most abundant MUP mRNAs in the liver (MUP I, II, and III) and in the lachrymal (MUP IV) and submaxillary (MUP V) glands. We have shown that these five mRNAs are coded by five distinct genes, MUP I through V. In the present communication, we examine the expression of MUP genes in all of the six tissues in which MUP mRNAs are synthesized, the mammary, parotid, sublingual, lachrymal, and submaxillary glands and the liver. We show that gene MUP II is expressed in the liver and in the mammary gland, that gene MUP IV is expressed in the lachrymal and parotid glands, and that gene MUP V is expressed in the submaxillary, sublingual, and lachrymal and parotid glands, and that gene MUP V is expressed in the submaxillary, sublingual, and lachrymal glands. Furthermore, we present evidence that in addition to genes MUP I through V, another gene, MUP VI, is expressed in BALB/c mice in the parotid gland. The tissue-specific synthesis of MUP mRNAs is thus brought about by two major mechanisms: the expression, in different tissues, of different members of the family and the expression of a single gene at various levels in different tissues. When a particular MUP gene is expressed in several tissues, transcripts of this gene initiate at the same site and are spliced and polyadenylated in the same manner.

Expression of six mouse major urinary protein genes in the mammary, parotid, sublingual, submaxillary, and lachrymal glands and in the liver

Mouse major urinary proteins (MUPs) are encoded by a family of about 35 to 40 highly conserved genes. In the preceding paper (K. Shahan, M. Gilmartin, and E. Derman, Mol. Cell. Biol. 7:1938-1946, 1987), we presented the sequences of the most abundant MUP mRNAs in the liver (MUP I, II, and III) and in the lachrymal (MUP IV) and submaxillary (MUP V) glands. We have shown that these five mRNAs are coded by five distinct genes, MUP I through V. In the present communication, we examine the expression of MUP genes in all of the six tissues in which MUP mRNAs are synthesized, the mammary, parotid, sublingual, lachrymal, and submaxillary glands and the liver. We show that gene MUP II is expressed in the liver and in the mammary gland, that gene MUP IV is expressed in the lachrymal and parotid glands, and that gene MUP V is expressed in the submaxillary, sublingual, and lachrymal and parotid glands, and that gene MUP V is expressed in the submaxillary, sublingual, and lachrymal glands. Furthermore, we present evidence that in addition to genes MUP I through V, another gene, MUP VI, is expressed in BALB/c mice in the parotid gland. The tissue-specific synthesis of MUP mRNAs is thus brought about by two major mechanisms: the expression, in different tissues, of different members of the family and the expression of a single gene at various levels in different tissues. When a particular MUP gene is expressed in several tissues, transcripts of this gene initiate at the same site and are spliced and polyadenylated in the same manner.

Nucleotide sequences of liver, lachrymal, and submaxillary gland mouse major urinary protein mRNAs: mosaic structure and construction of panels of gene-specific synthetic oligonucleotide probes

The mouse major urinary proteins (MUPs) are encoded by a gene family of about 35 to 40 members. MUPs are synthesized in at least six secretory tissues under a variety of developmental and endocrine controls, but the identities of the individual genes expressed in each tissue have not previously been established. In this article, we present the nucleotide sequences of five MUP mRNAs which we designate MUP I through V. MUPs I, II, and III are the most abundant MUP mRNA species in the liver, and MUPs IV and V are the most abundant MUP mRNA species in the lachrymal gland and the submaxillary gland, respectively. The sequence data show that each of the five mRNAs is encoded by a distinct member of the gene family. The structures of the MUP mRNA consist of interspersed segments of variable and conserved sequences. On the basis of the sequences of the variable segments, gene-specific panels of synthetic oligonucleotide probes were prepared. The gene-specific panels were used to identify cloned genes and, as described in the accompanying paper (K. Shahan, M. Denaro, M. Gilmartin, Y. Shi, and E. Derman, Mol. Cell. Biol. 7:1947-1954, 1987), to characterize the expression of MUP genes I through V.