The geographic distribution of monoamine oxidase haplotypes supports a bottleneck during the dispersion of modern humans from Africa

Every genetic locus mingles the information about the evolutionary history of the human species with the history of its own evolution. Therefore, to address the question of the origin of humans from a genetic point of view, evolutionary histories from many genetic loci have to be gathered and compared. We have studied two genes residing on the X chromosome encoding monoamine oxidases A and B (MAOA and MAOB). Both genes have been suggested to play a role in psychiatric and/or behavioral traits. To search for DNA variants of the MAO genes, the sequences of exonic and flanking intronic regions of these two genes were determined in a group of Swedish males. The sequence analysis revealed several novel polymorphisms in the MAO genes. Haplotypes containing high-frequency MAOA polymorphisms were constructed, and their frequencies were determined in additional samples from Caucasian, Asian, and African populations. We found two common haplotypes with similar frequencies in Caucasian and Asian populations. However, only one of them was also the most frequent haplotype in Africans, while the other haplotype was present in only one Kenyan male. This profound change in haplotype frequencies from Africans to non-Africans supports a possible bottleneck during the dispersion of modern humans from Africa.

High-resolution quantification of specific mRNA levels in human brain autopsies and biopsies

Quantification of mRNA levels in human cortical brain biopsies and autopsies was performed using a fluorogenic 5' nuclease assay. The reproducibility of the assay using replica plates was 97%-99%. Relative quantities of mRNA from 16 different genes were evaluated using a statistical approach based on ANCOVA analysis. Comparison of the relative mRNA levels between two groups of samples with different time postmortem revealed unchanged relative expression levels for most genes. Only CYP26A1 mRNA levels showed a significant decrease with prolonged time postmortem (p = 0.00004). Also, there was a general decrease in measured mRNA levels for all genes in autopsies compared to biopsies; however, on comparing mRNA levels after adjusting with reference genes, no significant differences were found between mRNA levels in autopsies and biopsies. This observation indicates that studies of postmortem material can be performed to reveal the relative in vivo mRNA levels of genes. Power calculations were done to determine the number of individuals necessary to detect differences in mRNA levels of 1.5-fold to tenfold using the strategy described here. This analysis showed that samples from at least 50 individuals per group, patients and controls, are required for high-resolution ( approximately twofold changes) differential expression screenings in the human brain. Experiments done on ten individuals per group will result in a resolution of approximately fivefold changes in expression levels. In general, the sensitivity and resolution of any differential expression study will depend on the sample size used and the between-individual variability of the genes analyzed.

Alpha-tectorin involvement in hearing disabilities: one gene--two phenotypes

The human alpha-tectorin (TECTA) gene has recently been cloned and proposed to be involved in autosomal dominant non-syndromic hearing impairment (NSHI) in two families linked to the DFNA12 locus. We have studied a Swedish pedigree with autosomal dominant NSHI with possible digenic inheritance of the disease, involving locus DFNA12 in chromosome 11 and locus DFNA2 in chromosome 1. Mutation analysis of the TECTA gene in this family has identified eight nucleotide substitutions indicating that TECTA is highly polymorphic. One of the changes results in a cysteine to serine (C 1057 S) mutation, in the zonadhesin domain of TECTA; this segregates with the disease haplotype on chromosome 11 and is not present in a control population. The mutation results in the replacement of a cysteine in one of the repeats of the zonadhesin/Von Willebrand domain of the protein and might cause a change in the crosslinking of the polypeptide. These findings add support to the involvement of TECTA in hearing disabilities. However, the three families carrying different TECTA mutations also show phenotypic differences: the hearing loss ranges from prelingual to progressive with late onset. The explanation for the different phenotypes and some clues regarding the functions of TECTA may lie in the localization of the mutations in the different modules of the protein. Another possibility is that the phenotype in the Swedish family is the result of two defective genes.

Evidence for digenic inheritance of nonsyndromic hereditary hearing loss in a Swedish family

We investigated a Swedish family with nonsyndromic progressive bilateral sensorineural hearing loss. Thirteen candidate loci for autosomal dominant nonsyndromic hearing loss were tested for linkage in this family. We found significant LOD scores (>3) for markers at candidate locus DFNA12 (11q22-q24) and suggestive LOD scores (>2) for markers at locus DFNA2 (1p32). Our results for markers on chromosome 11 narrowed down the candidate region for the DFNA12 locus. A detailed analysis of the phenotypes and haplotypes shared by the affected individuals supported the notion that two genes segregated together with hearing impairment in the family. Severely affected family members had haplotypes linked to the disease allele on both chromosomes 1 and 11, whereas individuals with milder hearing loss had haplotypes linked to the disease allele on either chromosome 1 or chromosome 11. These observations suggest an additive effect of two genes, each gene resulting in a mild and sometimes undiagnosed phenotype, but both together resulting in a more severe phenotype.

Linkage analysis of candidate loci in families with recurrent major depression

Recurrent major depression, RMD, is characterized by the occurrence of depressive episodes in the absence of mania and/or hypomania. In linkage studies, RMD (or, in general, unipolar depression) are frequently grouped together with bipolar illnesses into a broad definition of affective disorders. However, twin studies suggest that RMD and bipolar disorders might have different genetic determinants. The objective of this study was to test a set of families with RMD for linkage to chromosomes that have been recently proposed to contain susceptibility loci for bipolar disorders: chromosomes 16, 18, 21 and the short arm of chromosome 4. We analysed five large families from the northern part of Sweden ascertained through a proband with RMD and containing several patients with RMD. For the genetic analysis, we included only severely affected individuals (those who had at least three episodes that required medical treatment) to increase the chances of finding a larger degree of genetic determination. The genetic model led to a total disease prevalence of 5% in females and 3% in males. We did not find significant evidence for linkage to any of the candidate chromosomes in the combined family set. Only one of the families showed a slight indication for linkage with markers from the pericentromeric region of chromosome 18. A genome scan analysis on an extended collaborative family material with severely affected individuals with RMD should be performed to evaluate whether RMD and bipolar disorders have a different genetic etiology.

European Multicentre Association Study of Schizophrenia: a study of the DRD2 Ser311Cys and DRD3 Ser9Gly polymorphisms

As part of the European Multicentre Association Study of Schizophrenia (EMASS), we studied polymorphisms in the dopamine DRD2 and DRD3 receptor genes. The EMASS collaboration was established to create a large, statistically powerful sample of schizophrenic patients and controls from different European centres. Previous studies have suggested associations between schizophrenia and the Ser311Cys polymorphism in exon 7 of the dopamine DRD2 receptor gene [Arinami et al., (1994): Lancet 343:703-704] and a polymorphism Ser9gly in exon 1 of the dopamine DRD3 receptor gene [Crocq et al. (1992): J Med Genet 29:858-860]. We tested for these associations in samples of 373 and 413, and 311 and 306 patients and controls, respectively. We found no evidence for allelic association between schizophrenia and the Cys311 variant of the DRD2 receptor gene and no homozygotes for this variant were observed by any group. However, an excess of homozygotes for both alleles of the DRD3 polymorphism was observed in schizophrenic patients (chi2 = 8.54, P = 0.003, odds ratio = 1.64, 95% CI = 1.18-2.29). We also observed a significant excess of the 1-1 (Ser9Ser) genotype (chi2 = 8.13, P = 0.004, odds ratio = 1.7, 95% CI = 1.18-2.4). No evidence of heterogeneity between samples was detected and there was no evidence of an allelic association. These findings suggest that the rare Cys311 variant in exon 7 of the DRD2 receptor gene does not play a role in the pathogenesis of schizophrenia in European populations. Currently, our results do support the previous findings of an association between increased homozygosity of the Ser/Gly variant of the Dopamine D3 receptor gene and schizophrenia.

Mitochondrial sequence variants in patients with schizophrenia

To investigate whether mitochondrial mutations underly susceptibility to schizophrenia, we sequenced the mtDNAs of two unrelated Swedish patients with schizophrenia and low cytochrome oxidase activity and two maternally related Scottish patients from a family with suspected maternal inheritance of the disease. We found five substitutions in coding regions that have not previously been described as polymorphisms. These new substitutions were studied in 81 schizophrenic patients and five control groups from Sweden and Scotland and found to differ in frequency between populations, emphasizing the importance of using large and well-defined control materials for evaluating the association of mtDNA mutations with disease. The results do not lend strong support to the association of a particular mtDNA substitution with increased risk for schizophrenia. However, the trend towards a higher frequency of substitutions in the patients deserves further attention.

Embryonic expression of the mRNA for the rat homologue of the fusin/CXCR-4 HIV-1 co-receptor

We have previously cloned a human receptor recently shown to be a cofactor for entry of T-tropic HIV-1 strains into CD4+ cells, now named fusin. Stromal derived factor-1 (SDF-1) is an endogenous ligand for fusin, also called CXCR-4. Here we show the distribution of fusin/CXCR-4 mRNA during ontogeny in the rat. The onset of mRNA expression is around embryonic day 9 and the mRNA expression is high in the thymus as well as proliferative areas of the brain during development. Our results suggest: (1) that fusin/CXCR-4 might have a dual role in both brain development and the immune system; (2) that SDF-1 has a role in brain development or that additional physiological ligands exist for this receptor; (3) co-expression of CD4 and fusin/CXCR-4 may make fetuses susceptible to HIV infection during development.

Human brain contains high levels of heteroplasmy in the noncoding regions of mitochondrial DNA

We have analyzed the level of intraindividual sequence variability (heteroplasmy) of mtDNA in human brain by denaturing gradient gel electrophoresis and sequencing. Single base substitutions, as well as insertions or deletions of single bases, were numerous in the noncoding control region (D-loop), and 35-45% of the molecules from a single tissue showed sequence differences. By contrast, heteroplasmy in coding regions was not detected. The lower level of heteroplasmy in the coding regions is indicative of selection against deleterious mutations. Similar levels of heteroplasmy were found in two brain regions from the same individual, while no heteroplasmy was detected in blood. Thus, heteroplasmy seems to be more frequent in nonmitotic tissues. We observed a 7.7-fold increase in the frequency of deletions/insertions and a 2.2-fold increase in the overall frequency of heteroplasmic mutations in two individuals aged 96 and 99, relative to an individual aged 28. Our results show that intraindividual sequence variability occurs at a high frequency in the noncoding regions of normal human brain and indicate that small insertions and deletions might accumulate with age at a lower rate than large rearrangements.

Decreased cytochrome-c oxidase activity and lack of age-related accumulation of mitochondrial DNA deletions in the brains of schizophrenics

Defects in mitochondrial energy production have been implicated in several neurodegenerative disorders, such as Parkinson disease and amyotrophic lateral sclerosis. To study the contribution of mitochondrial defects to Alzheimer disease and schizophrenia, cytochrome-c oxidase (COX) activity and levels of the mtDNA4977 deletion in postmortem brain tissue specimens of patients were compared with those of asymptomatic age-matched controls. No difference in COX activity was observed between Alzheimer patients and controls in any of five brain regions investigated. In contrast, schizophrenic patients had a 63% reduction of the COX activity in the nucleus caudatus (P < 0.0001) and a 43% reduction in the cortex gyrus frontalis (P < 0.05) as compared to controls. The average levels of the mtDNA4977 deletion did not differ significantly between Alzheimer patients and controls, and the deletion followed similar modes of accumulation with age in the two groups. In contrast, no age-related accumulation of mtDNA deletions was found in schizophrenic patients. The reduction in COX activity in schizophrenic patients did not correlate with changes in the total amount of mtDNA or levels of the mtDNA4977 deletion. The lack of age-related accumulation of the mtDNA4977 deletion and reduction in COX activity suggest that a mitochondrial dysfunction may be involved in the pathogenesis of schizophrenia.

Trypanosoma cruzi exoantigen is a member of a 160 kDa gene family

During the chronic stage of Chagas disease a 160 kDa antigen appears in the blood of patients and remains detectable many years after the onset of the disease. This antigen is secreted by the trypomastigote form of the parasite while it is undetectable in the epimastigote form. We report here that the chronic 160 kDa exoantigen is encoded by a gene family (CEA 160 family). We describe the cloning and partial nucleotide sequence of a gene (CEA 160-1) belonging to the CEA160 family. Comparison of the gene sequence with other sequences present in the databases revealed homologies with several Trypanosoma cruzi surface antigens. Highest amino acid identity (59%) was with members of a family containing epitopes that mimic nervous tissues (Van Voorhis et al. 1993). Another related group (18-22% amino acid identity) comprises proteins of 85 or 160 kDa sharing an amino acid motif that is conserved among bacterial neuraminidases (Fouts et al. 1991; Pollevick et al. 1991; Kahn et al. 1991; Takle & Cross, 1991; Franco et al. 1993). The amino acid identities with the different antigens were not homogeneously distributed. Regions of higher identity (40-60%) were grouped in the central region of each protein.

Expression of peptide YY and mRNA for the NPY/PYY receptor of the Y1 subtype in dorsal root ganglia during rat embryogenesis

We have used in situ hybridization to study the distribution of mRNA for neuropeptide Y (NPY), peptide YY (PYY) and the NPY/PYY receptor of the Y1 subtype during ontogenesis in the rat and immunohistochemistry to analyse peptide immunoreactivity for NPY and PYY. We found that mRNA and immunoreactivity for NYY are transiently expressed in dorsal root ganglia (DRG) at embryonic day 16 (E16). In contrast, neither NPY mRNA nor NPY-like immunoreactivity were found in DRG at any developmental stage. The Y1 receptor mRNA is not expressed in DRG at E16 but it appears in these ganglia later in development (E20) and it is present in DRG of adult rats. In sagittal sections of whole embryos at very early stages of development we found that the onset of PYY mRNA expression is around day 11, when mRNA for PYY is found in the foregut. NPY and Y1-receptor mRNA are not detected in whole embryo sections until around day 14. Therefore, PYY mRNA expression precedes by 2-3 days the expression of mRNA for both NPY and the Y1 receptor. At E14, PYY mRNA is present in trigeminal ganglia and stomach. Our results suggest that PYY is not only a gut hormone but may also act as a neuropeptide with roles in the development of sensory neurons.

A proposed bovine neuropeptide Y (NPY) receptor cDNA clone, or its human homologue, confers neither NPY binding sites nor NPY responsiveness on transfected cells

Receptors with seven transmembrane domains (7TM) constitute a large family of structurally and functionally related proteins which respond to various types of ligands. We describe here the cloning and expression of a human 7TM receptor, denoted hFB22 (human Fetal Brain 22), which is the homologue (92% amino acid identity) of a bovine receptor (LCR1) reported by others to bind neuropeptide Y (NPY) with a pharmacological profile of the Y3 receptor subtype. However, upon expression in COS1 (confirmed by Northern analysis), COS7 or CHO-K1 cells, the hFB22 receptor did not confer specific 125I-Bolton-Hunter-NPY, 3H-propionyl-NPY or 125I-peptide YY (PYY) binding sites, in either intact cells or in membrane preparations. Similarly, cells transfected with the corresponding bovine clone (LCR1) did not show specific NPY/PYY binding exceeding that resulting from endogenous binding sites; mock-transfected COS7 cells, used frequently for heterologous expression of receptors, were found to have endogenous specific 125I-NPY binding sites (Bmax = 112 fmol/mg protein; Kd = 0.25 nM). Moreover, the hFB22 transfected cells, when compared to control transfected cells, did not display de novo NPY- or PYY-induced second messenger responses, i.e., (1) inhibition of forskolin-stimulated cAMP accumulation or (2) 45Ca2+ influx. The presence of hFB22 mRNA was detected in several human neuroblastoma cell lines, none of which was found to express Y3-like NPY binding sites. hFB22 displays 39% amino acid sequence identity (in the transmembrane regions) to the human interleukin-8 receptor, and 32-36% amino acid identity to the human receptors of angiotensin II, bradykinin, and n-formylpeptide, but only 23% amino acid identity to the previously described human NPY/PYY receptor of the Y1 receptor subtype. Our results show that hFB22 and LCR1 do not encode NPY receptors, and their true ligand(s) remains to be identified.

Estrogen control of uterine tissue factor messenger ribonucleic acid levels

One of the early responses of the immature rat uterus to stimulation by estradiol (E2) is an increase in the specific activity and synthesis of a discrete set of proteins including tissue factor (TF). Increases in TF are associated with stimulation of cell growth in mouse and human fibroblasts and endothelial cells. The increase in TF activity following E2 stimulation of the uterus is due to an increase in TF messenger RNA (mRNA). A 2- to 4-fold increase in mRNA is observed 1 h after injection, reaches a maximum at 3 h, and is reduced at 6 h. The increase is hormone specific and occurs at low levels of E2 (0.66 micrograms/kg). The E2 effect is abolished by actinomycin but not by cycloheximide. The changes in TF mRNA occur in a similar time scale and at similar E2 doses as the increases in the uterine proto-oncogenes c-jun and c-fos.

Estrogen regulation of a tissue factor-like procoagulant in the immature rat uterus

An estrogen-responsive procoagulant activity is present in the plasma membrane fraction of immature rat uterus. This procoagulant has many of the properties of tissue factor, a widely occurring, integral membrane protein which initiates the intrinsic pathway of coagulation. Procoagulant activity was demonstrated to activate prothrombin in rat uterus, to activate human coagulation factor X, and to cause clot formation by human plasma. Procoagulant activity could be solubilized from the plasma membrane by the detergent octyl glucoside and had an apparent mol wt of 20,000-40,000 by gel filtration. Procoagulant activity was increased 4-fold within 3 h after immature rats were injected with estradiol. The increase was tissue- and hormone specific and was not affected by a warfarin-induced vitamin K deficiency. Coagulation factor VII was required for clot formation by the procoagulant. These properties are consistent with identification of the procoagulant as tissue factor. mRNA for tissue factor was increased in the uterus 3 h after estrogen stimulation. In the preceding paper we showed that prothrombin is increased in the immature uterus within 3 h of estrogen stimulation. The presence of increased amounts of a tissue factor-like procoagulant in the same time period suggests a functional relationship between these two proteins and a possible role for both in uterine development. Thrombin is a growth factor in fibroblasts and endothelial cells. We propose that after estrogen stimulation, prothrombin enters the uterus with the influx of plasma proteins and is activated by the procoagulant to thrombin. We suggest that thrombin might act as a paracrine factor early in the estrogen-stimulated development of the uterus.

Prothrombin levels are increased in the estrogen-treated immature rat uterus

An estrogen-responsive uterine proenzyme of a proteinase in the immature rat uterus has been known for some time. Its mol wt is 77,000, its N-terminal amino acid sequence is the same as prothrombin's for 15 residues, it contains gamma-carboxyl glutamate residues, its biosynthesis is prevented by warfarin, it cross-reacts with antibodies to human and rat prothrombin, and it can be activated by human factor Xa or a uterine procoagulant. The products of activation, when separated on sodium dodecyl sulfate-gels, react with antibodies to human or rat prothrombin to give bands that have mol wt corresponding to those of the products of activation of prothrombin. These activation intermediates hydrolyze synthetic substrates specific for thrombin and have the same mol wt as the activation products of prothrombin. The proteinase generated in the activation has the following properties of thrombin: it is inhibited by hirudin and PheProArg-chloromethyl ketone, it has kinetic constants similar to those of thrombin with tripeptide p-nitroanilides as substrates, and it digests actin to give the same peptides as thrombin. We conclude that the uterine proenzyme is prothrombin. The time course of the prothrombin response to estrogen suggests that prothrombin enters the uterus as part of the transudation of plasma proteins that occurs after estrogen stimulation. A membrane-bound uterine procoagulant that activates uterine prothrombin also increases in response to estrogen stimulation. We propose that the simultaneous increase in these two activities results in a localized generation of thrombin, a well characterized mitogen in fibroblasts and epithelial cells. Our results suggest that thrombin may have a vital function as a mitogen in the early steps of the estrogen-stimulated hypertrophy and hyperplasia of the immature uterus.

Variable number of repeat units in genes encoding Trypanosoma cruzi antigens

The genes encoding a protein antigenic during the acute phase (SAPA) and another one antigenic during the chronic phase (antigen 30) of human Chagas' disease were analyzed in 15 Trypanosoma cruzi isolates and clones collected in distant geographical regions. These two genes had tandem repeats which were present in all parasites tested. However, large differences in the length of restriction fragments were observed among isolates. This was readily explained by variations in the number of repeat units present in homologous genes. This result was confirmed after analysis of 3 members of the SAPA gene family. In the case of antigen 30, we propose that differences in the number of repeat units result in size differences in the corresponding RNAs and proteins, which explains the large size heterogeneity in otherwise homologous T. cruzi antigens.

Separation and identification of two components of an estrogen-responsive, calcium-dependent arginine esteropeptidase

Arginine esteropeptidase is an estrogen-responsive, calcium-dependent enzyme in rat uterine cytosol. It appears in increased amounts 3 h after administration of physiologic amounts of 17 beta-estradiol to an immature female rat. Its reaction was resolved into two parts: a calcium-dependent activation of the enzyme and a calcium-independent hydrolysis of the substrate. The esteropeptidase was separated by DEAE cellulose chromatography into two components. The properties of component A, the activator, are distinct from those of component B, the enzyme, which has the same response to inhibitors as serine proteinases. Both components are subject to estrogen control. Component A is present in significant amounts only after estrogen stimulation. Component B is increased 3-fold after estrogen stimulation. The responses of the two components to inhibitors, their different molecular weights and chromatographic behavior and the pH optima of their reactions distinguish them from each other and from other uterine proteinases previously described.