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Query: UNIPROT:P06889 (Mol)
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A comparative study between microsatellite and allozyme markers was conducted on natural populations of resident brown trout (Salmo trutta) sampled over a reduced geographical scale and on hatchery strains. The higher level of polymorphism observed at microsatellite loci resulted in higher power of statistical tests for differentiation among population samples and for genotypic linkage disequilibrium. Genetic distances of Cavalli-Sforza and Edwards were on average two times larger for microsatellites than for allozymes but multilocus FST estimates computed over the entire set of populations were not significantly different for both categories of markers. Assignment tests of individual fish to the set of sampled populations demonstrated a much higher efficiency of microsatellites compared to allozymes. Pairwise multilocus FST estimates were significantly correlated to waterway distances and there was a significant tendency for the incorrectly classified individuals to be assigned to one of the nearest populations, indicating that isolation-by-distance acted significantly on brown trout populations. This increase of differentiation with distance was higher for allozymes than for microsatellites. Traditional measures of genetic differentiation (Cavalli-Sforza and Edwards' chord distance and FST) were compared for microsatellites to recently proposed statistics taking into account allele size differences (Goldstein's distance and PST). Using Goldstein's distance for neighbour-joining analysis did not improve the tree structure resolution. Multilocus estimates of PST and FST were not significantly different when computed over the entire set of populations but no significant correlation was detected between matrices of pairwise multilocus PST estimates and waterway distances.
Mol Ecol 1998 Mar
PMID:Comparative analysis of microsatellite and allozyme markers: a case study investigating microgeographic differentiation in brown trout (Salmo trutta). 956 90

Wright's FST and related statistics are often used to measure the extent of divergence among populations of the same species relative to the net genetic diversity within the species. This paper compares several definitions of FST which are relevant to DNA sequence data, and shows that these must be used with care when estimating migration parameters. It is also pointed out that FST is strongly influenced by the level of within-population diversity. In situations where factors such as selection on closely linked sites are expected to have stronger effects on within-population diversity at some loci than at others, differences among loci can result entirely from differences in within-population diversities. It is shown that several published cases of differences in FST among regions of high and low recombination in Drosophila may be caused in this way. For the purpose of comparisons of levels of between-population differences among loci or species which are subject to different intensities of forces that reduce variability within local populations, absolute measures of divergence between populations should be used in preference to relative measures such as FST.
Mol Biol Evol 1998 May
PMID:Measures of divergence between populations and the effect of forces that reduce variability. 958 Sep 82

Activins are part of the intragonadal factors that can modulate the actions of gonadotropins and regulate cellular functions during preantral or early antral stages of folliculogenesis in vivo. In a mouse early preantral follicle culture system, activin A production was measured and recombinant bovine activin A (r-ACT A) was added (10 or 50 ng/ml) to recombinant follicle-stimulating hormone (r-FSH)-supplemented (10 or 100 mIU/ml) medium for a 12-day culture period. Specificity of activin A action was ascertained by addition of recombinant human follistatin (r-FA; 20 or 100 ng/ml). Immunoreactive activin A concentrations in mouse follicle-conditioned medium increased by a factor of 20-50, reaching concentrations from 2 to 5 ng/ml at end of culture. In the initial days of culture, additions of r-ACT A to r-FSH-supplemented medium provoked a dramatic volumetric increase and earlier attachment of the follicle. A dose of 100 ng/ml r-FS was able to block the actions of 10 ng/ml but not those caused by 50 ng/ml r-ACT A. In follicle cultures supplemented with 10 mIU/ml r-FSH, additions of r-ACT induced a dose-dependent inhibin (INH) and estradiol (E2) increase. Basal and human chorionic gonadotropin (HCG)-induced progesterone (P) production were not influenced by r-ACT A or r-FS additions. Addition of r-ACT A decreased (P = 0.017) the intact follicle survival rate and had no influence on final oocyte diameter. In cultures supplemented by 10 mIU/ml r-FSH, additions of r-ACT A did not influence progression and resumption of meiosis I. Use of a higher r-FSH supplementation dose (100 mIU/ml) tended to affect meiosis I adversely (P = 0.052), and r-ACT A addition amplified this effect significantly (P = 0.007). These in vitro experiments demonstrate pronounced effects from r-ACT on r-FSH-mediated follicle survival, growth, and estrogen biosynthesis.
Mol Reprod Dev 1998 Jul
PMID:Effects of recombinant activin A on in vitro culture of mouse preantral follicles. 962 5

The population structure of variation in a nuclear actin intron and the control region of mitochondrial DNA is described for humpback whales from eight regions in the North Pacific Ocean: central California, Baja Peninsula, nearshore Mexico (Bahia Banderas), offshore Mexico (Socorro Island), southeastern Alaska, central Alaska (Prince Williams Sound), Hawaii and Japan (Ogasawara Islands). Primary mtDNA haplotypes and intron alleles were identified using selected restriction fragment length polymorphisms of target sequences amplified by the polymerase chain reaction (PCR-RFLP). There was little evidence of heterogeneity in the frequencies of mtDNA haplotypes or actin intron alleles due to the year or sex composition of the sample. However, frequencies of four mtDNA haplotypes showed marked regional differences in their distributions (phi ST = 0.277; P < 0.001; n = 205 individuals) while the two alleles showed significant, but less marked, regional differences (phi ST = 0.033; P < 0.013; n = 400 chromosomes). An hierarchical analysis of variance in frequencies of haplotypes and alleles supported the grouping of six regions into a central and eastern stock with further partitioning of variance among regions within stocks for haplotypes but not for alleles. Based on available genetic and demographic evidence, the southeastern Alaska and central California feeding grounds were selected for additional analyses of nuclear differentiation using allelic variation at four microsatellite loci. All four loci showed significant differences in allele frequencies (overall FST = 0.043; P < 0.001; average n = 139 chromosomes per locus), indicating at least partial reproductive isolation between the two regions as well as the segregation of mtDNA lineages. Although the two feeding grounds were not panmictic for nuclear or mitochondrial loci, estimates of long-term migration rates suggested that male-mediated gene flow was several-fold greater than female gene flow. These results include and extend the range and sample size of previously published work, providing additional evidence for the significance of genetic management units within oceanic populations of humpback whales.
Mol Ecol 1998 Jun
PMID:Population structure of nuclear and mitochondrial DNA variation among humpback whales in the North Pacific. 964 Jun 50

In passerine birds morphological differentiation in bill size within species is not commonly observed. Bill size is usually associated with a trophic niche, and strong differences in it may reflect the process of genetic differentiation and, possibly, speciation. We used both mitochondrial DNA (mtDNA) and nuclear microsatellites to study genetic variation between two subspecies of reed bunting, Emberiza schoeniclus schoeniclus and E.s. intermedia, along their distributional boundary in western Europe. These two subspecies are characterized by a high dimorphism in bill size and, although breeding populations of the two subspecies are found very close to each other in northern Italy, apparently no interbreeding occurs. The observed morphological pattern between the two subspecies may be maintained by geographically varying selective forces or, alternatively, may be the result of a long geographical separation followed by a secondary contact. MtDNA sequences of cytochrome b and ND5 (515 bp) showed little variation and did not discriminate between the two subspecies, indicating a divergence time of less than 500 000 years. The analysis of four microsatellite loci suggested a clear, although weak, degree of genetic differentiation in the large- and small-billed populations, as indicated by FST and RST values and genetic distances. The correlation between bill size and genetic distance between populations remained significant after accounting for the geographical distances between sampling localities. Altogether, these results indicate a very recent genetic differentiation between the two bill morphs and suggest that a strong selection for large bills in the southern part of the breeding range is probably involved in maintaining the geographical differentiation of this species.
Mol Ecol 1998 Sep
PMID:Genetic variation and bill size dimorphism in a passerine bird, the reed bunting Emberiza schoeniclus. 973 74

Whisker pad innervation and whisker-specific pattern formation were examined in mice lacking the gene for activin betaA or for follistatin. Both strains of mice die within 24 h after birth. A normal array of whisker follicles is present in the snout of either phenotype. However, activin betaA-deficient mice lack whiskers, and in follistatin-deficient mice the whiskers are thin and curled. We examined the effects of aberrant, albeit innervated, follicles on the formation of whisker-specific patterns (barrelettes) in the trigeminal brainstem. Activin betaA knockout mice lack barrelettes, although the trigeminal afferent topography is not compromised. Physiological recordings suggest that trigeminal ganglion cells in these mice are less responsive to stimulation of whisker follicles. Barrelettes in follistatin-deficient mice are not as well developed as in controls, but can be discerned in some cases. These results are consistent with the notion that formation of barrelettes depends on neural activity initiated by the whiskers.
Mol Cell Neurosci 1998 Nov
PMID:Defective whisker follicles and altered brainstem patterns in activin and follistatin knockout mice. 982 86

Recent studies have revealed that islet cells differentiate from the epithelial cells of primitive pancreatic ducts during embryogenesis, and can regenerate in response to the loss of islet cells even in adult pancreas. The ability of islet cells to regenerate raises the possibility that impaired and decreased islets of diabetic patients can be restored. In this review, factors regulating islet development including differentiation factors (Shh, activin, follistatin, and TGF alpha), transcriptional factors (PDX1, Isl1, Pax4, Pax6, Nkx2.2, Nkx6.1, BETA2, and HNF), growth factors (the EGF family, HGF, IGF-I, IGF-II, Reg, INGAP, PDGF, FGF, VEGF, and NGF), hormones (insulin, the GH family, PTHrP, TRH, and gastrin), and cell adhesion molecules (N-CAM and cadherins) are described after a short introduction and an outline of pancreatic development.
Int J Mol Med 1999 Mar
PMID:Development of pancreatic islets (review). 1002 48

This study of wild-living Algerian Barbary macaques (Macaca sylvanus) was designed to examine genetic variability in subpopulations isolated in residual forest patches, in an attempt to obtain data on the effects of habitat fragmentation. The wild population of this species (estimated at a maximum of 15,000) is vulnerable and this study therefore has direct relevance for conservation measures. Data from five microsatellite loci were analysed for 159 individuals from nine different groups living in four isolates in Algeria. Genetic polymorphism was found to be relatively high (4-12 alleles per locus) compared with other genetic markers used in previous studies of this species; mean expected heterozygosity was 65%. The four isolates are all genetically distinct (FST = 0; P < 0.001). Indeed, the results suggest that dispersal is limited even between some social groups within a single isolate. Genetic distances based on models not assuming stepwise mutation (FST and chord distance) gave very similar results and are highly correlated with geographical distances within one isolate but not between isolates. This may indicate that isolation by distance exerts a significant influence within an isolate but that genetic drift prevails between the four isolates. After allowing for variation in sample size, we found no evidence of reduced allelic diversity within small isolates that may have been separated for 250 years or more. The surviving population of Algerian Barbary macaques taken as a whole still shows marked variability in microsatellite alleles, but maintenance of genetic variability over the long term will surely require effective protection of all isolates.
Mol Ecol 1999 Mar
PMID:Genetic differentiation within and between isolated Algerian subpopulations of Barbary macaques (Macaca sylvanus): evidence from microsatellites 1019 7

Activin, and its binding protein, follistatin, are up-regulated by mediators of inflammation, and recent studies have demonstrated that activin A can block the activity of the key inflammatory cytokine, interleukin-6 (IL-6). These findings thereby implicate activin and follistatin in the control of the inflammatory cascade. In this study, interactions between interleukin-1beta (IL-1beta), IL-6 and activin were examined the human liver cell line, HepG2, for their effect on cell proliferation and the production of the acute phase proteins, haptoglobin and alpha1-acid glycoprotein (alpha1-AGP). IL-1beta and activin A, but not IL-6, inhibited the proliferation of HepG2 cells. Activin A together with IL-1beta caused a greater inhibition of proliferation than either factor alone, and the inhibitory effects of activin A were blocked by the addition of follistatin to the cultures. Activin A alone inhibited the production of haptoglobin but did not affect alpha1-AGP concentrations. However, activin A suppressed the stimulatory effects of IL-6 on the production of both haptoglobin and alpha1-AGP. Production of follistatin by HepG2 cells was stimulated by activin A, but was inhibited by both IL-1beta and IL-6, indicating a complex regulatory loop is operable to modulate the effects of activin A during inflammation. Taken together, these data suggest that activin A interacts with IL-1beta and IL-6 to regulate and coordinate the production of acute phase proteins during an inflammatory episode.
Mol Cell Endocrinol 1999 Feb 25
PMID:Activin A regulates growth and acute phase proteins in the human liver cell line, HepG2. 1022 78

FSH is required to maintain FSH and LH/hCG receptors at elevated steady-state levels after receptor induction. Although this function of FSH is mediated by cAMP, how cAMP level is related to the maintenance of gonadotropin receptors is unknown. To investigate cAMP's effect on changes in the levels of FSH receptor mRNAs in rat granulosa cells, total RNA from cells was prepared and analyzed by Northern blots. Incubation with 8-Br-cAMP for 24 h produced a dose-related increase in FSH receptor mRNA in granulosa cells of DES-primed immature rats. On the other hand, 8-Br-cAMP, washed at 24 h, exerted inverse dose-related effects on FSH receptor mRNA levels at 96 h. The addition of 1 mM cAMP resulted in higher levels of FSH receptor mRNA than that induced by 0.2 mM cAMP at 24 h, while 0.2 mM cAMP is as effective as 1-2 mM cAMP for the induction of FSH receptor mRNA at 96 h. To further analyze cAMP's role in the production of activin in granulosa cells, we measured activin levels in the culture medium after the addition of 8-Br-cAMP. The levels of activin A were suppressed by the addition of 8-Br-cAMP in a dose-dependent manner. In addition, the procedure by which 8-Br-cAMP was removed after 24 h incubation showed that the level of activin in the medium increased after medium change. With regard to the actions of activin A on gonadotropin receptors, our laboratory has demonstrated that activin A increases the levels of FSH receptor mRNAs. Therefore, cAMP has a negative effect on FSH receptor expression by suppressing the activin level. Since follistatin production is up-regulated by cAMP in this system, we examined the effect of follistatin on FSH receptor mRNA level, which is induced by activin and FSH. Cotreatment with follistatin (0-100 ng/ml) and activin (50 ng/ml) in the presence of FSH (30 ng/ml) caused a significant reduction in FSH receptor mRNA levels induced by activin. Based on these observations, it is possible that cAMP has both stimulatory and inhibitory effects on the expression of gonadotropin receptors, and the overall influence of cAMP on their expression might be determined by the integration of such opposing effects.
Mol Cell Endocrinol 1999 Mar 25
PMID:Control of FSH receptor mRNA expression in rat granulosa cells by 3',5'-cyclic adenosine monophosphate, activin, and follistatin. 1037 19


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