Changes among wild House mice (Mus musculus) bred for ten generations in a cold environment, and their evolutionary implications

Wild House mice, Mus musculus , bred at 23°C (controls) changed little in reproductive performance over ten generations. Similar mice bred at 3°C (Eskimo) became more fertile and heavier. Eskimo body fat also rose. Control adrenal weights declined; Eskimo adrenal weights were heavier than those of controls, but only during the first four generations. The Eskimo phenotype after ten generations was a combined result of a direct response to cold, parental effects and genetical changes in the Eskimo population. Maternal effects were probably especially important. In such conditions, the minimum unit of selection that it is useful to consider is the female and her litter.     

Evolution of Escherichia coli in different carbon environments for 2,000 generations

Cellular energetics is thought to have played a key role in dictating all major evolutionary transitions in the history of life on Earth. However, how exactly cellular energetics and metabolism come together to shape evolutionary paths is not well understood. In particular, when an organism is evolved in different energy environments, what are the phenomenological differences in the chosen evolutionary trajectories, is a question that is not well understood. In this context, starting from an Escherichia coli K‐12 strain, we evolve the bacterium in five different carbon environments—glucose, arabinose, xylose, rhamnose and a mixture of these four sugars (in a predefined ratio) for approximately 2,000 generations. At the end of the adaptation period, we quantify and compare the growth dynamics of the strains in a variety of environments. The evolved strains show no specialized adaptation towards growth in the carbon medium in which they were evolved. Rather, in all environments, the evolved strains exhibited a reduced lag phase and an increased growth rate. Sequencing results reveal that these dynamical properties are not introduced via mutations in the precise loci associated with utilization of the sugar in which the bacterium evolved. These phenotypic changes are rather likely introduced via mutations elsewhere on the genome. Data from our experiments indicate that evolution in a defined environment does not alter hierarchy in mixed‐sugar utilization in bacteria.     

Adrenocortical function in mice selectively bred for different sensitivity to ethanol

The adrenocortical response to ethanol, histamine and electric shock was studied in the Short-Sleep (SS) and Long-Sleep (LS) mice. The plasma corticosterone levels measured at 60 min following ethanol injection were consistently higher in LS mice (males and females) than in SS mice. The corticosterone levels determined 60 min after histamine injection (50 mg/kg) or electric foot shock were not statistically different in these two lines of mice. The initial rise of the corticosteroid after ethanol injection was identical in SS and LS mice, whereas the costicosteroid response to mild stress of saline injection was different: SS mice showed higher levels of corticosterone than LS mice at 20 and 30 min after the injection. Corticosterone increment attributable to alcohol stress clearly seemed greater in LS than in SS mice, even though the adrenals of the SS mice were 20–30% heavier than those of LS. The possible significance of these endocrine differences with respect to sensitivity to ethanol and behavioral arousal level was discussed.     

Nematospiroides dubius: multiple infections in mice bred for immune responsiveness

Allogeneic mice were reared over 5 generations in a 2-way selection for high (H) and low (L) immune responsiveness to the intestinal trichostrongylid nematode Nematospiroides dubius. After 5 generations of selective breeding, the H mice passed fewer N. dubius eggs and harbored fewer, smaller and less fecund worms than did the L mice. These trends were observed after each of 4 consecutive infections, which were all treated with levamisole before reinfection. Further, more H than L mice were worm-free, and H mice were sensitized to sterile immunity by fewer infections than were needed by the L mice. These results encourage the view that the selective breeding of host species of agricultural importance is a valuable means of biologic control of nematodiasis.     

Hippocampal RNA sequencing in mice selectively bred for high and low activity

High and Low Activity strains of mice were bidirectionally selected for differences in open-field activity (DeFries et al., 1978, Behavior Genetics, 8: 3–13) and subsequently inbred to use as a genetic model for studying anxiety-like behaviors (Booher et al., 2021, Genes, Brain and Behavior, 20: e12730). Hippocampal RNA-sequencing of the High and Low Activity mice identified 3901 differentially expressed protein-coding genes, with both sex-dependent and sex-independent effects. Functional enrichment analysis (PANTHER) highlighted 15 gene ontology terms, which allowed us to create a narrow list of 264 top candidate genes. Of the top candidate genes, 46 encoded four Complexes (I, II, IV and V) and two electron carriers (cytochrome c and ubiquinone) of the mitochondrial oxidative phosphorylation process. The most striking results were in the female high anxiety, Low Activity mice, where 39/46 genes relating to oxidative phosphorylation were upregulated. In addition, comparison of our top candidate genes with two previously curated High and Low Activity gene lists highlight 24 overlapping genes, where Ndufa13, which encodes the supernumerary subunit A13 of complex I, was the only gene to be included in all three lists. Mitochondrial dysfunction has recently been implicated as both a cause and effect of anxiety-related disorders and thus should be further explored as a possible novel pharmaceutical treatment for anxiety disorders.     

QTL mapping for fiber quality traits across multiple generations and environments in upland cotton

Identification of quantitative trait loci (QTL) for fiber quality traits that are stable across multiple generations and environments could facilitate marker-assisted selection for improving cotton strains. In the present study, F₂, F_2:3, and recombinant inbred lines (RILs, F _6:8 ) populations derived from an upland cotton (Gossypium hirsutum L.) cross between strain 0-153, which has excellent fiber quality, and strain sGK9708, a commercial transgenic cultivar, were constructed for QTL tagging of fiber quality. We used 5,742 simple sequence repeat primer pairs to screen for polymorphisms between the two parent strains. Linkage maps of F₂ and RILs were constructed, containing 155 and 190 loci and with a total map distance of 959.4 centimorgans (cM) and 700.9?cM, respectively. We screened fiber quality QTL across multiple generations and environments through composite interval mapping of fiber quality data. Specifically, we studied F₂ and F_2:3 family lines from Anyang (Henan Province) in 2003 and 2004 and RILs in Anyang in 2007 and Anyang, Quzhou (Hebei Province), and Linqing (Shandong Province) in 2008. We identified 50 QTL for fiber quality: 10 for fiber strength, 10 for fiber length, 10 for micronaire, eight for fiber uniformity, and 12 for fiber elongation. Nine of these fiber quality QTL were identified in F₂, F_2:3 and RILs simultaneously. Two QTL for fiber strength on chromosomes C7 and C25 were detected in all three generations and all four environments and explained 16.67?C27.86% and 9.43?C21.36% of the phenotypic variation, respectively. These stable QTL for fiber quality traits could be used for marker assisted selection.     

Partial trisomy 10p in two generations

Summary Two cases of partial 10p trisomy due to a t(10;20)(p12;p12) in two generations of a family are presented. Analysis of 20 known cases of such aberrations confirmed the opinion of Schleiermacher et al. (1974) that partial trisomy 10p is a distinct clinically recognizable entity. The most important diagnostic features of this syndrome are dolichocephaly, prominent forehead, wide open sutures and fontanelles, broad root of the nose, cleft lip and palate, clubfoot, and cystic changes in kidneys.     

Y-to-X chromosome translocation observed in two generations

Summary A family is reported in which the mother and two sons are carriers of a Y-X translocation. The distal segment of the short arm of the X chromosome appears to have been deleted to give place to a translocation of the distal part of the long arm of the Y chromosome. Apart from short stature the mother is essentially free of stigmata, while the sons show a combination of mental retardation, hypertelorism, simian creases, clinodactyly, scanty palmar lines, and dry fragile skin. The cases described are discussed against the background of the few known previously published cases.     

Trisomy 21 mosaicism in two subjects from two generations.

In the course of a chromosome fragility investigation on the cancer prone hereditary disorder xeroderma pigmentosum, a low proportion of cells with a 47,XY,+21 karyotype was found in lymphocyte cultures of a patient not showing any Down syndrome symptom. The presence of trisomy 21 mosaicism was demonstrated also in peripheral blood of the healthy father and confirmed by "chromosome painting" that allowed a rapid detection of chromosomes 21 on metaphase cells and interphase nuclei. The trisomic cell line was not detected in fibroblast cultures. The analysis of chromosome 21 heteromorphism indicated that in both subjects the mosaic could result from either a diploid or an aneuploid zygote. Since in the trisomic cell line of the father and the son the extra chromosome 21 seems to be the same, a predisposition toward mitotic errors (non-disjunction or anaphase lagging) may be postulated, leading to the recurrent gain or loss of a specific chromosome 21. In order to test the hypothesis of an abnormal mitotic behaviour of the chromosome 21, we investigated the centromere separation index and the DNA restriction pattern in Southern blots probed with satellite DNA sequences specific for chromosome 21 centromere. Both the approaches did not reveal any peculiar feature that may account for the genetically determined proneness to mitotic error observed in the family.     

Genetic consequences of many generations of hybridization between divergent copepod populations

Crosses between populations of the copepod Tigriopus californicus typically result in outbreeding depression. In this study, replicate hybrid populations were initiated with first generation backcross hybrids between two genetically distinct populations from California: Royal Palms (RP) and San Diego (SD). Reciprocal F(1) were backcrossed to SD, resulting in expected starting frequencies of 25% RP/75% SD nuclear genes on either a pure RP cytoplasmic or a pure SD cytoplasmic background. After 1 year of hybridization (up to 15 generations), seven microsatellite loci were scored in two replicates on each cytoplasmic background. Frequencies of the rarer RP alleles increased significantly in all four replicates, regardless of cytoplasmic source, producing a mean hybridity of 0.97 (maximum = 1), instead of the expected 0.50. Explicit tests for heterozygote excess across loci and replicates showed significant deviations. Only the two physically linked markers showed linkage disequilibrium in all replicates. Subsequent fitness assays in parental populations and early generation hybrids revealed lower fitness in RP than SD, and significant F(2) breakdown. Computer simulations showed that selection must be invoked to explain the shift in allele frequencies. Together, these results suggest that hybrid inferiority in early generations gave way to hybrid superiority in later generations.     

Listeria monocytogenes adheres to many materials found in food-processing environments

AIMS: To investigate the adhesion of Listeria monocytogenes 10403S to 17 different, food-use approved materials representing metals, rubbers and polymers. METHODS AND RESULTS: Adhesion assays were conducted by placing 'coupons' of the materials in planktonic cultures at 30 degrees C, and then immediately withdrawing them ('short contact') or leaving them submerged in the cultures for 2 h. Adherent cells were recovered by sonication. In the short contact experiments, the logarithm of the mean viable counts ranged from 3.67 +/- 0.43 to 4.78 +/- 0.38. After 2 h contact time, the numbers of adherent cells had increased significantly for all materials with the exception of polypropylene. The highest count (6.33 +/- 0.31) recorded was for stainless steel 405. CONCLUSION: Adhesion to a wide range of materials was time-dependent and characterized by reversible and irreversible stages. SIGNIFICANCE AND IMPACT OF THE STUDY: Adhesion test protocols must account for cell carry-over and cells which are only weakly bound. Material selection may only have a limited role in reducing food contamination by listeria.     

Anxiety-related defensive behavioral responses in mice selectively bred for High and Low Activity

High and Low Activity strains of mice (displaying low and high anxiety-like behavior, respectively) with 7.8–20 fold differences in open-field activity were selected and subsequently inbred to use as a genetic model for studying anxiety-like behavior in mice (DeFries et al., 1978, Behavior Genetics, 8:3-13). These strains exhibited differences in other anxiety-related behaviors as assessed using the light–dark box, elevated plus-maze, mirror chamber, and elevated square-maze tests (Henderson et al., 2004, Behavior Genetics, 34: 267-293). The purpose of these experiments was three-fold. First, we repeated a 6-day behavioral battery using updated equipment and software to confirm the extreme differences in anxiety-like behaviors. Second, we tested novel object exploration, a measure of anxiety-like behavior that does not rely heavily on locomotion. Third, we conducted a home cage wheel running experiment to determine whether these strains differ in locomotor activity in a familiar, home cage environment. Our behavioral test battery confirmed extreme differences in multiple measures of anxiety-like behaviors. Furthermore, the novel object test demonstrated that the High Activity mice exhibited decreased anxiety-like behaviors (increased nose pokes) compared to Low Activity mice. Finally, male Low Activity mice ran nearly twice as far each day on running wheels compared to High Activity mice, while female High and Low Activity mice did not differ in wheel running. These results support the idea that the behavioral differences between High and Low Activity mice are likely to be due to anxiety-related factors and not simply generalized differences in locomotor activity.     

Sensitivity to psychostimulants in mice bred for high and low stimulation to methamphetamine

Methamphetamine (MA) and cocaine induce behavioral effects primarily through modulation of dopamine neurotransmission. However, the genetic regulation of sensitivity to these two drugs may be similar or disparate. Using selective breeding, lines of mice were produced with extreme sensitivity (high MA activation; HMACT) and insensitivity (low MA activation; LMACT) to the locomotor stimulant effects of acute MA treatment. Studies were performed to determine whether there is pleiotropic genetic influence on sensitivity to the locomotor stimulant effect of MA and to other MA- and cocaine-related behaviors. The HMACT line exhibited more locomotor stimulation in response to several doses of MA and cocaine, compared to the LMACT line. Both lines exhibited locomotor sensitization to 2 mg/kg of MA and 10 mg/kg of cocaine; the magnitude of sensitization was similar in the two lines. However, the lines differed in the magnitude of sensitization to a 1 mg/kg dose of MA, a dose that did not produce a ceiling effect that may confound interpretation of studies using higher doses. The LMACT line consumed more MA and cocaine in a two-bottle choice drinking paradigm; the lines consumed similar amounts of saccharin and quinine, although the HMACT line exhibited slightly elevated preference for a low concentration of saccharin. These results suggest that some genes that influence sensitivity to the acute locomotor stimulant effect of MA have a pleiotropic influence on the magnitude of behavioral sensitization to MA and sensitivity to the stimulant effects of cocaine. Further, extreme sensitivity to MA may protect against MA and cocaine self-administration.     

Fish oil supplementation for two generations increases insulin sensitivity in rats

We investigated the effect of fish oil supplementation for two consecutive generations on insulin sensitivity in rats. After the nursing period (21 days), female rats from the same prole were divided into two groups: (a) control group and (b) fish oil group. Female rats were supplemented with water (control) or fish oil at 1 g/kg body weight as a single bolus for 3 months. After this period, female rats were mated with male Wistar rats fed on a balanced chow diet (not supplemented). Female rats continued to receive supplementation throughout gestation and lactation periods. The same treatment was performed for the next two generations (G1 and G2). At 75 days of age, male offspring from G1 and G2 generations from both groups were used in the experiments. G1 rats did not present any difference with control rats. However, G2 rats presented reduction in glycemia and lipidemia and improvement in in vivo insulin sensitivity (model assessment of insulin resistance, insulin tolerance test) as well as in vitro insulin sensitivity in soleus muscle (glucose uptake and metabolism). This effect was associated with increased insulin-stimulated p38 MAP kinase phosphorylation and lower n-6/n-3 fatty acid ratio, but not with activation of proteins from insulin signaling (IR, IRS-1 and Akt). Global DNA methylation was decreased in liver but not in soleus muscle. These results suggest that long-term fish oil supplementation improves insulin sensitivity in association with increased insulin-stimulated p38 activation and decreased n-6:n-3 ratio in skeletal muscle and decreased global DNA methylation in liver.