Chromosomal and regional localization of the loci for IGKC,IGGC, ALDB,HOXB, GPT,and PRNP in the American mink (Mustela vison): comparisons with human and mouse

Chromosomal localization of the genes for gamma- and kappa-immunoglobulins (IGGC and IGKC, respectively), aldolase B (ALDB), prion protein (PRNP), homeo box B (HOXB), and glutamate pyruvate transaminase (GPT) were determined with the use of mink-rodent hybrid cells. Analysis of segregation of the mink markers and chromosomes in these hybrid cells allowed us to assign the gene for HOXE to Chromosome (Chr) 8, IGGC to Chr 10, PRNP and IGKC to Chr 11, ALDB to Chr 12, and GPT to Chr 14 in mink. Furthermore, using a set of mink-mouse hybrid cells carrying fragments of mink Chr 8 of different sizes, we assigned the gene for HOXB to the pter-p26 region of the short arm of Chr 8. Comparative mapping of the genes of mink, human, and mouse, as well as other mammalian species, demonstrated that the mink genes HOXB, PRNP, ALDB, and IGGC are members of a conserved region shared by many mammalian species in common; the IGKC gene is a member of a conserved region common to carnivores and primates, not rodents; the GPT gene is a member of a syntenic gene group probably unique to the Mustelidae family or carnivores.     

Cotransfer and phenotypic stabilisation of syntenic and asyntenic mink genes into mouse cells by chromosome-mediated gene transfer

Summary By means of metaphase chromosomes, the genes for mink thymidine kinase (TK) and hypoxanthine-phosphoribosyltransferase (HPRT) were transferred to mutant mouse cells, LMTK^-, A9 (HPRT^-) and teratocarcinoma cells, PCC4-aza 1 (HPRT^-). Eighteen colonies were isolated from LMTK^- (series A), 9 from A9 (series B) and none from PCC4-aza 1. The transformed clones contained mink TK or HPRT. Analysis of syntenic markers in series B demonstrated that one clone contained mink glucose-6-phosphate dehydrogenase (G6PD) and the other alpha-galactosidase; in series A, nine clones contained mink galactokinase (GALK) and six mink aldolase C (ALDC). Analysis of 12 asyntenic markers located in ten mink chromosomes showed the presence of only aconitase-1 (ACON1) (the marker of mink chromosome 12) in three clones of series A. The clones lost mink ACON1 between the fifth to tenth passages. Cytogenetic analysis established the presence of a fragment of mink chromosome 8 in eight clones of series A, but not in series B. The clones of series A lost mink TK together with mink GALK and ALDC during back-selection; in B, back-selection retained mink G6PD. No stable TK⁺ phenotype was detected in clones with a visible fragment of mink chromosome 8. Stability analysis demonstrated that about half of the clones of series B have stable HPRT⁺ phenotype whereas only three clones of series A have stable TK⁺ phenotype. It is suggested that the recipient cells, LMTK^- and A9, differ in their competence for genetic transformation and integration of foreign genes.     

Fates and expression ofBacillus subtilis endo-β-1, 4-glucanase gene andAlcaligenes faecalis β-glucosidase gene introduced inEscherichia coli andBacillus cells

Summary Two kinds of cellulase genes coding for endo--1, 4-glucanase and -glucosidase, isolated fromBacillus subtilis andAlcaligenes faecalis respectively, were separately or combinedly put on a newly constructedEscherichia coli-Bacillus shuttle vector plasmid. When the recombinant plasmids having cellulase gene(s) were introduced intoE. coli orBacillus cells, drastic differences in fates and expression of the two genes were observed.     

Startle-evoked changes in diaphragmatic activity during wakefulness and sleep

Tonic inhibition of some respiratory muscles occurs as part of the generalized muscle atonia of rapid-eye-movement sleep (REMS). A second type of inhibition of the diaphragm during REMS, fractionations, consists of brief pauses in the diaphragmatic electromyogram (DIA EMG) in association with phasic events. Because motor inhibition can occur as part of the startle response, and the brain is highly activated during REMS, we hypothesized that the neural basis of the fractionations might be activation of a startle network. To test this hypothesis, tone bursts (100 dB, 20-ms duration at 15-s intervals) were applied to cats at a fixed inspiratory level in the DIA moving average during REMS, non-rapid-eye-movement sleep (NREMS), and wakefulness. Parallel sham studies (no tone applied) were obtained for each state. The response of the DIA EMG was averaged over 100 ms by using the tone pulse as a trigger, and the following parameters of the DIA EMG were measured: latency to peak and/or nadir, increment or decrement in activity, and duration of peak and/or nadir. After a tone, all five animals studied displayed a profound suppression of DIA activity during REMS (latency to nadir 42.4 +/- 10.0 ms, duration of suppression 35.9 +/- 17.6 ms). Similarly, DIA activity was suppressed in all cats during NREMS (latency to nadir 40.9 +/- 13.3 ms, duration 23.9 +/- 13.4 ms). An excitatory response was observed in only two cats during NREMS and wakefulness. The similarity of startle-induced DIA EMG pauses to spontaneous fractionations of DIA activity during REMS suggests that the latter result from activation of a central startle system.     

Substitution of serine for alpha 1(I)-glycine 844 in a severe variant of osteogenesis imperfecta minimally destabilizes the triple helix of type I procollagen. The effects of glycine substitutions on thermal stability are either position of amino acid specific

Recent reports have demonstrated that a series of probands with severe osteogenesis imperfecta had single base mutations in one of the two structural genes for type I procollagen that substituted amino acids with bulkier side chains for glycine residues and decreased the melting temperature of the triple helix. Here we demonstrate that the type I procollagen synthesized by cultured fibroblasts from a proband with a severe form of osteogenesis imperfecta consisted of normal molecules and molecules over-modified by post-translational reactions. The thermal stability of the intact type I collagen was normal as assayed by protease digestion under conditions in which a decrease in thermal stability was previously observed with eight other substitutions for glycine in the alpha 1(I) chain. In contrast, the thermal stability of the one-quarter length B fragment generated by digestion with vertebrate collagenase was decreased by 2-3 degrees C under the same conditions. Nucleotide sequencing of cDNAs and genomic DNA established that the proband had a substitution of A for G in one allele of the pro alpha 1(I) gene that converted the codon for alpha 1-glycine 844 to a codon for serine. The results also established that the alpha 1-serine 844 was the only mutation that could account for the decrease in thermal stability of the collagenase B fragment. There are at least two possible explanations for the failure of the alpha 1-serine 844 substitution to decrease the thermal stability of the collagen molecule whereas eight similar mutations decreased the melting temperature. One possibility is that the effects of glycine substitutions are position specific because not all glycine residues make equivalent contributions to cooperative blocks of the triple helix that unfold in the predenaturation range of temperatures. A second possible explanation is that substitutions of glycine by serine have much less effect on the stability of protein than the substitutions by arginine, cysteine, and aspartate previously studied.     

INBREEDING DEPRESSION IN ANDRODIOECIOUS POPULATIONS OF DATISCA GLOMERATA (DATISCACEAE)

Several workers have suggested that the rarity of androdioecy (the presence of males and hermaphrodites in a breeding population) in nature is due to the large fitness gain required by male plants in order to be maintained by selection. As part of an ongoing investigation of this hypothesis, we tested the effects of selfing on fitness in functionally androdioecious populations of Datisca glomerata. We compared progeny from self-fertilizations, cross-fertilizations with pollen from male plants only, cross-fertilizations with pollen from hermaphrodite plants only, and open-pollinated flowers for several measures of progeny fitness including seed weight, germination rate, and seedling weight. Significant inbreeding depression was observed for androdioecious populations of D. glomerata for both seed and seedling weights. However, no significant differences were observed across treatments for seed germination percentages. The observation of significant levels of inbreeding depression in this study, combined with prior evidence of threefold greater pollen production by males, may at least partially account for the large fitness increase required by males to be maintained by selection.     

Chromosomal and regional localization of the genes for UMPH2, APRT, PEPD, PEPS, PSP, and PGP in mink: comparison with man and mouse

Segregation of mink biochemical markers uridine 5'-monophosphate phosphohydrolase-2 (UMPH2), adenine phosphoribosyltransferase (APRT), phosphoserine phosphatase (PSP), phosphoglycolate phosphatase (PGP), peptidases D (PEPD) and S (PEPS), as well as mink chromosomes, was investigated in a set of mink x mouse hybrid clones. The results obtained allowed us to make the following mink gene assignments: UMPH2, chromosome 8; PEPD and APRT, chromosome 7; PEPS, chromosome 6; and PSP and PGP, chromosome 14. The latter two genes are the first known markers for mink chromosome 14. For regional mapping, UMPH2 was analyzed in mouse cell clones transformed by means of mink metaphase chromosomes (Gradov et al., 1985) and also in mink x mouse hybrid clones carrying fragments of mink chromosome 8 of different sizes. Based on the data obtained, the gene for UMPH2 was assigned to the region 8pter----p26 of mink chromosome 8. The present data is compared with that previously established for man and mouse with reference to the conservation of syntenic gene groups and G-band homoeologies of chromosomes in mammals.     

Subchromosomal localization and order of GLA, PGK1, HPRT, and G6PD loci on the X chromosome of the American mink (Mustela vison)

Segregation of the X-linked mink markers alpha-galactosidase (GLA), phosphoglycerate kinase-1 (PGK1), hypoxanthine phosphoribosyltransferase (HPRT), and glucose-6-phosphate dehydrogenase (G6PD) was analyzed in hybrids of gamma-irradiated mink fibroblasts and Chinese hamster cells and in hybrids of nonirradiated mink fibroblasts and mouse hepatoma cells. Based on this analysis, the order of the four genes is GLA-PGK1-HPRT-G6PD on the mink X chromosome. Cytogenetic analysis of five mink x Chinese hamster hybrid clones containing mink GLA, PGK1, and HPRT, but lacking G6PD, tentatively localized mink G6PD to Xq15.22----qter and also confirmed the gene order as GLA-PGK1-HPRT-G6PD-qter. Comparison of this order with its counterpart in man and the mouse, as well as an analysis of the G-band patterns of their X chromosomes, demonstrated putative similarities between mink and man and differences in the mouse. These differences may be due to a different rate of X-chromosomal rearrangement in mammalian evolution.