Social isolation-induced epigenetic changes in midbrain of adult mice

Social isolation and loneliness increase the risk of death as much as well-established risk factors for mortality such as cigarette smoking and alcohol consumption. The underlying molecular mechanisms are poorly understood. In the present study, 3 months old male C57BL/6 mice were socially isolated by individual housing for another 3 months. At the age of 6 months, epigenetic changes were analyzed in midbrain. Social isolation of male adult mice led to an increased global DNA methylation, which was associated with enhanced activity of DNA methyltransferase. Di- and trimethylation of global histone H3 lysine 4 (H3K4) were increased in midbrain of socially isolated mice, accompanied by enhanced H3K4 histone methyltransferase activity. In addition, social isolation of adult mice led to activation of histone acetyltransferases as well as of histone deacetylases (HDAC) resulting in a net enhancement of histone H3 lysine 9 (H3K9) acetylation. Gene-specific effects were observed for Hdac1, Hdac3 and the serotonin transporter Slc6a4. Social isolation led to an up-regulation of Hdac1 and Hdac3, associated with decreased DNA methylation in the CpG island of the respective genes. On the contrary, the Slc6a4 gene was down-regulated, which was associated with enhanced DNA methylation. Collectively, the results from the present study demonstrate for the first time that social isolation of adult mice leads to a wide range of global epigenetic changes and these effects may have profound impact on gene expression pattern and phenotype of the socially isolated animals.

Disruption of the ATE1 and SLC12A1 Genes by Balanced Translocation in a Boy with Non-Syndromic Hearing Loss

We report on a boy with non-syndromic hearing loss and an apparently balanced translocation t(10;15)(q26.13;q21.1). The same translocation was found in the normally hearing brother, father and paternal grandfather; however, this does not exclude its involvement in disease pathogenesis, for example, by unmasking a second mutation. Breakpoint analysis via FISH with BAC clones and long-range PCR products revealed a disruption of the arginyltransferase 1 (ATE1) gene on translocation chromosome 10 and the solute carrier family 12, member 1 gene (SLC12A1) on translocation chromosome 15. SNP array analysis revealed neither loss nor gain of chromosomal regions in the affected child, and a targeted gene enrichment panel consisting of 130 known deafness genes was negative for pathogenic mutations. The expression patterns in zebrafish and humans did not provide evidence for ear-specific functions of the ATE1 and SLC12A1 genes. Sanger sequencing of the 2 genes in the boy and 180 GJB2 mutation-negative hearing-impaired individuals did not detect homozygous or compound heterozygous pathogenic mutations. Our study demonstrates the many difficulties in unraveling the molecular causes of a heterogeneous phenotype. We cannot directly implicate disruption of ATE1 and/or SLC12A1 to the abnormal hearing phenotype; however, mutations in these genes may have a role in polygenic or multifactorial forms of hearing impairment. On the other hand, it is conceivable that our patient carries a disease-causing mutation in a so far unidentified deafness gene. Evidently, disruption of ATE1 and/or SLC12A1 gene function alone does not have adverse effects.

FTO and INSIG2 Genotyping Combined with Metabolic and Anthropometric Phenotyping of Morbidly Obese Patients

Obesity is a major health problem worldwide. Associations of obesity with common variants of the fat mass- and obesity-associated gene (FTO) and insulin-induced gene 2 (INSIG2) have been reported in various studies. We aimed to further investigate the association of 2 single nucleotide polymorphisms (SNPs), rs9939609 in FTO and rs7566605 in INSIG2, with body mass index (BMI) and other anthropometric and metabolic parameters in subjects with morbid obesity (BMI ≥40). SNPs rs9939609 and rs7566605 were genotyped in 124 unrelated morbidly obese patients (mean BMI = 50, range 40.1-77.1) from Mainz, Germany, and in 253 normal controls without a history of morbid obesity. Metabolic and anthropometric parameters were analyzed in 109 of the 124 patients, and associations with the genotype data were examined. The high-risk AA genotype for FTO rs9939609 was observed in 32.3% of patients versus 15.8% of controls (p = 0.0004) and was associated with an increased obesity risk [odds ratio (OR) = 2.54, 95% confidence interval (CI) = 1.53-4.21]. The intermediate-risk AT genotype was found in patients and controls at similar frequencies (48.4 vs. 48.6%, OR = 0.99). The low-risk TT genotype for rs9939609 was found in 19.4% of patients (35.5% of controls; p = 0.0013) and was associated with a decreased risk for morbid obesity (OR = 0.43, CI = 0.26-0.73). In contrast, INSIG2 rs7566605 showed no association with obesity in our patients. Evaluation of metabolic data indicated associations between the high-risk FTO genotype (rs9939609_AA) and increased levels of serum glutamic oxaloacetic transaminase (GOT) and between the high-risk INSIG2 genotype (rs7566605_CC) and lower waist-to-hip ratio and lower hemoglobin A1c (HbA1c) levels. Our results confirm an association of the FTO SNP with extreme obesity. However, we found no association of the potential obesity risk allele of INSIG2 in our sample and thus cannot confirm an association of the INSIG2 CC genotype with obesity. We identified an association between the high-risk FTO genotype (rs9939609_AA) and higher GOT levels, which could possibly reflect the increased frequency of nonalcoholic steatohepatitis with obesity. We also detected associations of the high-risk INSIG2 genotype (rs7566605_CC) with lower waist-to-hip ratios and lower HbA1c levels, which may indicate amelioration of impaired glucose tolerance and type 2 diabetes for patients with this genotype after bariatric surgery.

Prenatal Clinical Assessment of sFlt-1 (Soluble fms-like Tyrosine Kinase-1)/PlGF (Placental Growth Factor) Ratio as a Diagnostic Tool for Preeclampsia, Pregnancy-induced Hypertension, and Proteinuria

Background: Aim of the study was a critical assessment of the clinical validity of the prenatal determination of sFlt-1/PlGF for preeclampsia (PE), pregnancy-induced hypertension (PIH), and proteinuria. Our analysis was based on a specificity of 95 % and a sensitivity of 82 % for the prediction of preeclampsia, as described by Elecsys (Roche). Methods: In this retrospective study the ratio of the prenatal antiangiogenic factor sFlt-1 (soluble fms-like tyrosine kinase-1) to the proangiogenic factor PIGF (placental growth factor) was analyzed using the electrochemiluminescence immunoassay of Elecsys (Roche Diagnostics, Mannheim, Germany) in 173 pregnant women. Sixty-three women with PE, 34 women with PIH and 6 women with proteinuria were compared to 72 controls. On average, the sFlt-1/PlGF ratio was determined 8 (controls), 2.4 (PE), 3.2 (PIH) and 4.1 (proteinuria) weeks before delivery. The PE and PIH cases were further subdivided into early (< 34 weeks of gestation) and late (≥ 34 weeks of gestation) onset groups. Statistical data analysis was done using the usual descriptive statistics and logistic regression analysis. ROC curves were calculated, and the sensitivity, specificity, and negative and positive predictive value (NPV, PPV) were estimated for a threshold of 85. Results: Although the specificity of the sFlt-1/PlGF ratio was high for PE, the sensitivity was low (only 59.4 %), thus giving unsatisfying results for PE. The sensitivity only increased to 62.5 % for the early-onset PE group. Intriguingly, a high ratio was detected for the combination of IUGR (intrauterine growth restriction) and PE in the early-onset PE group (8 cases). In the control group, 4 cases exceeded the cut-off value of 85 but showed no clinical signs of PE and the birth was unremarkable. In summary, we found that the sFlt-1/PIGF ratio could not be used as a predictive test for preeclampsia but rather as an indicator for the development and estimation of the severity of PE. Thus, the test is less suitable for the reliable exclusion of PE in routine clinical practice. Recommendation: The determination of the sFlT-1/PlGF ratio is only one element for PE diagnosis in addition to the measurement of blood pressure, proteinuria, ultrasound and Doppler.

Novel VANGL1 Gene Mutations in 144 Slovakian, Romanian and German Patients with Neural Tube Defects

Neural tube defects (NTDs) are a group of congenital malformations of the central nervous system occurring at an average rate of 1 per 1,000 human pregnancies worldwide. Numerous genetic and environmental factors are discussed to be relevant in their etiology. In mice, mutants in >200 genes including the planar cell polarity (PCP) pathway are known to cause NTDs, and recently, heterozygous mutations in the human VANGL1 gene have been described in a small subset of patients with NTDs. We performed a VANGL1 mutation analysis in 144 unrelated individuals with NTDs from Slovakia, Romania and Germany and identified 3 heterozygous missense mutations: c.613G>A (p.Gly205Arg) with an open spina bifida (lumbosacral meningomyelocele), c.557G>A (p.Arg186His) with a closed spina bifida (tethered cord and spinal lipoma) and c.518G>A (p.Arg173His) with an unknown NTD. The c.613G>A mutation was also found in a healthy sibling. None of the mutations were described previously. Findings support that heterozygous VANGL1 mutations represent hypomorphs or conditional mutants predisposing to NTDs and occur at a frequency of approximately 2.1% of open and closed spinal NTDs. The mutations (p.Arg173His, p.Arg186His, p.Gly205Arg) modified conserved regions of the VANGL1 protein and shared similarities with previously described mutants, providing further evidence for the presence of mutational hot spots in these patients.

Methylation and expression analyses of the 7q autism susceptibility locus genes MEST , COPG2, and TSGA14 in human and anthropoid primate cortices

The autism susceptibility locus on human chromosome 7q32 contains the maternally imprinted MEST and the non-imprinted COPG2 and TSGA14 genes. Autism is a disorder of the 'social brain' that has been proposed to be due to an overbalance of paternally expressed genes. To study regulation of the 7q32 locus during anthropoid primate evolution, we analyzed the methylation and expression patterns of MEST, COPG2, and TSGA14 in human, chimpanzee, Old World monkey (baboon and rhesus macaque), and New World monkey (marmoset) cortices. In all human and anthropoid primate cortices, the MEST promoter was hemimethylated, as expected for a differentially methylated imprinting control region, whereas the COPG2 and TSGA14 promoters were completely demethylated, typical for transcriptionally active non-imprinted genes. The MEST gene also showed comparable mRNA expression levels in all analyzed species. In contrast, COPG2 expression was downregulated in the human cortex compared to chimpanzee, Old and New World monkeys. TSGA14 either showed no differential regulation in the human brain compared to chimpanzee and marmoset or a slight upregulation compared to baboon. The human-specific downregulation supports a role for COPG2 in the development of a 'social brain'. Promoter methylation patterns appear to be more stable during evolution than gene expression patterns, suggesting that other mechanisms may be more important for inter-primate differences in gene expression.

Evaluating the effect of spastin splice mutations by quantitative allele-specific expression assay

BACKGROUND

mutations in the SPG4/SPAST gene are the most common cause for hereditary spastic paraplegia (HSP). The splice-site mutations make a significant contribution to HSP and account for 17.4% of all types of mutations and 30.8% of point mutations in the SPAST gene. However, only few studies with limited molecular approach were conducted to investigate and decipher the role of SPAST splice-site mutations in HSP.

METHODS

a reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and quantitative allele-specific expression assay were performed.

RESULTS

we have characterized the consequence of two novel splice-site mutations (c.1493 + 1G>A and c.1414-1G>A) in the SPAST gene in two different families with pure HSP. The RT-PCR analysis revealed that both spastin mutations are indeed splice-site mutations and cause skipping of exon 12. Furthermore, RT-PCR data suggested that these splice-site mutations may cause leaky splicing. By means of a quantitative allele-specific expression assay, we could confirm that both splice-site mutations cause leaky splicing, as the relative expression of the exon 12-skipped transcript was reduced (21.1 ± 3.6 compared to expected 50%).

CONCLUSIONS

our finding supports a "threshold-effect-model" for functional spastin in HSP. A higher level (78.8 ± 3.9%) of functional spastin than the expected ratio of 50% owing to leaky splicing might cause late age at onset of HSP. Remarkably, we could show that a quantitative allele-specific expression assay is a simple and effective tool to evaluate the role of most types of spastin splice-site mutations in HSP.

Epigenetic profile of developmentally important genes in bovine oocytes

Assisted reproductive technologies are associated with an increased incidence of epigenetic aberrations, specifically in imprinted genes. Here, we used the bovine oocyte as a model to determine putative epigenetic mutations at three imprinted gene loci caused by the type of maturation, either in vitro maturation (IVM) in Tissue Culture Medium 199 (TCM) or modified synthetic oviduct fluid (mSOF) medium, or in vivo maturation. We applied a limiting dilution approach and direct bisulfite sequencing to analyze the methylation profiles of individual alleles (DNA molecules) for H19/IGF2, PEG3, and SNRPN, which are each associated with imprinting defects in humans and/or the mouse model, and are known to be differentially methylated in bovine embryos. Altogether, we obtained the methylation patterns of 203 alleles containing 4,512 CpG sites from immature oocytes, 213 alleles with 4,779 CpG sites from TCM-matured oocytes, 215 alleles/4,725 CpGs in mSOF-matured oocytes, and 78 alleles/1,672 CpGs from in vivo-matured oocytes. The total rate of individual CpGs and entire allele methylation errors did not differ significantly between the two IVM and the in vivo group, indicating that current IVM protocols have no or only marginal effects on these critical epigenetic marks. Furthermore, the mRNA expression profiles of the three imprinted genes and a panel of eight other genes indicative of oocyte competence were determined by quantitative real-time PCR. We found different mRNA expression profiles between in vivo-matured oocytes versus their in vitro-matured counterparts, suggesting an influence on regulatory mechanisms other than DNA methylation.

261 INFLUENCE OF IN VITRO MATURATION ON EPIGENETIC MARKS AND GENE EXPRESSION IN BOVINE OOCYTES

In cattle, in vitro maturation (IVM) of oocytes is an integral part of assisted reproduction technology. However, only 30% of in vitro matured bovine oocytes develop to the blastocyst stage after fertilization (compared with 60% for in vivo matured oocytes), indicating critical involvement of maturation conditions in the developmental competence of oocytes. Oocytes for IVF and intracytoplasmic sperm injection in humans are typically allowed to mature in vivo after superovulation because IVM is not considered to be a safe medical procedure. Several studies have shown that assisted reproduction technology involving prolonged in vitro culture of human and ruminant embryos can be associated with increased risk of fetal or placental abnormalities due to aberrant DNA methylation of imprinted and non-imprinted genes. Similarities between the bovine large offspring syndrome and imprinting-related human Beckwith–Wiedemann syndrome and the general similarity of bovine and human pre-implantation development make bovine oocyte maturation and embryonic development an increasingly accepted model of human development. Differentially methylated regions and imprinting control regions for the bovine paternally imprinted gene H19 and the maternally imprinted genes PEG3 and SNRPN were identified and characterised in this study. The DNA methylation profiles of bovine oocytes could be determined by bisulfite treatment of DNA from pools of 10 oocytes, but no significant differences were observed between IVM in TCM medium with 20% O2, in SOF medium with 5% O2, or after in vivo maturation. In contrast, quantitative PCR analysis of single oocyte preparations (n ≥ 8) revealed significant differences between these groups in the expression of the 3 genes. We then investigated the expression of genes involved in other critical processes in the developing oocyte and early embryo by quantitative PCR, including SLC2A8 (glucose transport), GDF9 (growth factor), PRDX1 (antioxidant and intercellular communication), DNMT1a/b (maintenance of methylation), and DNMT3a/b (de novo methylation). We also studied IGF2R, an imprinted gene implicated in large offspring syndrome. We observed significant differences in the expression of several of these genes. Interestingly, the expression of DNMT3a and DNMT3b was significantly higher in in vitro matured oocytes than in in vivo matured oocytes and could result in the above-mentioned aberrant methylation patterns established later in embryonic development. This work was funded by DFG (FOR1041).

Characterization of differentially methylated regions in 3 bovine imprinted genes: a model for studying human germ-cell and embryo development

Correct imprinting is crucial for normal fetal and placental development in mammals. Experimental evidence in animal models and epidemiological studies in humans suggest that assisted reproductive technologies (ARTs) can interfere with imprinted gene regulation in gametogenesis and early embryogenesis. Bos taurus is an agriculturally important species in which ARTs are commonly employed. Because this species exhibits a similar preimplantation development and gestation length as humans, it is increasingly being used as a model for human germ-cell and embryo development. However, in contrast to humans and mice, there is relatively little information on bovine imprinted genes. Here, we characterized the bovine intergenic IGF2-H19 imprinting control region (ICR) spanning approximately 3 kb. We identified a 300-bp differentially methylated region (DMR) approximately 6 kb upstream of the H19 promoter, containing a CpG island with CTCF-binding site and high sequence similarity with the human intergenic ICR. Additional differentially methylated CpG islands lie -6 kb to -3 kb upstream of the promoter, however these are less conserved. Both classical bisulfite sequencing and bisulfite pyrosequencing demonstrated complete methylation of the IGF2-H19 ICR in sperm, complete demethylation in parthenogenetic embryos having only the female genome, and differential methylation in placental and somatic tissues. In addition, we established pyrosequencing assays for the previously reported bovine SNRPN and PEG3 DMRs. The observed methylation patterns were consistent with genomic imprinting in all analyzed tissues/cell types. The identified IGF2-H19 ICR and the developed quantitative methylation assays may prove useful for further studies on the relationship between ARTs and imprinting defects in the bovine model.

Spatial learning and expression patterns of PP1 mRNA in mouse hippocampus

BACKGROUND

Synaptic plasticity is believed to be the major cellular basis for learning and memory. Protein phosphorylation is a key process involved in changes in the efficacy of neurotransmission. In long-term changes synaptic plasticity is followed by structural plasticity and protein de novo synthesis. Such mechanisms are believed to build the basis of hippocampal learning and memory investigated in the Morris water maze (MWM) task. To examine the role of dephosphorylation during that model for spatial learning, we analyzed protein phosphatase 1 (PP1) expression in the hippocampus of mice at various stages of the task and in two groups with different learning abilities.

METHODS

Mice were trained for 4 days with four trials each day in the MWM. For gene expression hippocampi were prepared 1, 6 and 24 h after the last trial of each day. PP1 and brain-derived neurotrophic factor (BDNF) mRNA levels were determined by quantitative real-time PCR.

RESULTS

The task requirements themselves affected expression levels of both PP1 and BDNF. In contrast to BDNF, PP1 was differentially expressed during learning. Poorly and well performing mice differed significantly. When performance was poor the expression level of PP1 was higher.

CONCLUSION

Present results add further in vivo evidence that not only phosphorylation but also dephosphorylation is a major mechanism involved in learning and memory. Therefore, inhibition of hippocampal phosphatase activity might improve learning and memory.

340 EPIGENETIC ANALYSIS OF DEVELOPMENTALLY IMPORTANT GENES IN BOVINE OOCYTES OF DIFFERENT ORIGINS

A critical step in assisted reproductive technologies (ART) is the IVM of oocytes. The quality of the oocyte is crucial for successful fertilization and subsequent embryo development. Studies in bovine ART, and epidemiological studies in children from ART, reveal a degree of abnormal development thought to be primarily caused by aberrant DNA methylation patterns in imprinted and non-imprinted genes. Due to the inherent similarities in bovine and human preimplantation embryonic development, bovine oocyte and embryo development is increasingly being used as a model for human development. The goal of this project is to investigate the effects of specific IVM conditions on the DNA methylation profile of bovine oocytes and early embryos and to determine the relationship between DNA methylation and mRNA expression for selected developmentally important genes (PEG3, IGF2R, SNRPN, GDF9, Glut8, PRDX1, Dnmt1A and Dnmt3a/b). Two different IVM systems have been established, the first is the routinely used TCM-199 medium at 39°C, 5% CO2 in air, the second uses synthetic oviduct fluid medium (SOF) as the basic medium with minor modifications (10 mM glucose, 1 mM glutamine) at 39°C, 5% CO2 and reduced oxygen tension (5%). Oocytes for IVM were retrieved by slicing of ovaries collected from local slaughterhouses. Successful maturation was confirmed by extrusion of the first polar body for 78% (TCM) and 72% (SOF) of the oocytes, respectively. Results of quantitative real-time PCR experiments indicate that transcripts of the maternally imprinted gene PEG3 and the paternally imprinted gene IGF2R as well as transcripts of other developmentally important genes (GDF9, PRDX1 and Glut8) are present in immature and IVM oocytes and are applicable targets for further expression and methylation studies. Relative quantification of mRNA transcripts normalised to an external standard revealed that, while expression of the maternally imprinted PEG3 gene is lower in all groups of oocytes (immature: 9.8, matured in TCM: 3.3, and in SOF: 6.4), compared to the paternally imprinted IGF2R (immature: 29.3, TCM: 14.2, SOF: 19.2), no significant difference between the both groups of IVM oocytes could be detected. However, determination of specific effects of IVM will require more replicates and the comparison with IVM oocytes. This is currently underway and together with the ongoing methylation analysis based on the novel identification of differentially methylated regions in bovine imprinted genes, this study will provide deeper insight into the epigenetic profile of bovine oocytes as a potential causative mechanism implicated in the increased incidence of developmental abnormalities in human and bovine ART. Funded by DFG Research Unit Germ Cell Potential.

Haploinsufficiency of 16.4 Mb from chromosome 22pter-q11.21 in a girl with unilateral conductive hearing loss

We present the postnatal diagnosis of a de novo der(18)t(18;22)(p11.32;q11.21)pat, resulting in an unbalanced 45,XX,der (18)t(18;22) karyotype in a girl with conductive hearing loss on the left and ptosis of the right upper eye-lid. Unilateral ptosis was also observed in the patient's 2 years and 8 months younger sister, who grows noticeably faster and appears to be a much quicker learner. After speech therapy the patient was eventually placed in normal school. The haploinsufficient 16.4-Mb region on chromosome 22pter-->q11.21 contains 10 genes as well as many predicted genes, pseudogenes, and retrotransposed sequences with unknown functions. This observation may prove useful for prenatal diagnosis and genetic counselling of chromosome 22q11.1 gains and losses.

Epimutation at human chromosome 14q32.2 in a boy with a upd(14)mat-like clinical phenotype

Recently, three reports described deletions and epimutations affecting the imprinted region at chromosome 14q32.2 in individuals with a phenotype typical for maternal uniparental disomy of chromosome 14 [upd(14)mat]. In this study, we describe another patient with upd(14)mat-like phenotype including low birth weight, neonatal feeding problems, muscular hypotonia, motor and developmental delay, small hands and feet, and truncal obesity. Conventional cytogenetic analyses, fluorescence in situ hybridization subtelomere screening, multiplex ligation-dependent probe amplification analysis of common microdeletion and microduplication syndromes, and methylation analysis of SNRPN all gave normal results. Methylation analysis at 14q32.2 revealed a gross hypomethylation of the differentially methylated regions (intergenic DMR and MEG3-DMR). Further molecular studies excluded full or segmental upd(14)mat as well as a microdeletion within this region. Evidently, the upd(14)mat-like clinical phenotype is caused by an epimutation at 14q32.2. The clinical and molecular features of this novel case are discussed with respect to the recently published cases.

Two independent chromosomal rearrangements, a very small (550 kb) duplication of the 7q subtelomeric region and an atypical 17q11.2 (NF1) microdeletion, in a girl with neurofibromatosis

Most patients with neurofibromatosis (NF1) are endowed with heterozygous mutations in the NF1 gene. Approximately 5% show an interstitial deletion of chromosome 17q11.2 (including NF1) and in most cases also a more severe phenotype. Here we report on a 7-year-old girl with classical NF1 signs, and in addition mild overgrowth (97th percentile), relatively low OFC (10th-25th percentile), facial dysmorphy, hoarse voice, and developmental delay. FISH analysis revealed a 17q11.2 microdeletion as well as an unbalanced 7p;13q translocation leading to trisomy of the 7q36.3 subtelomeric region. The patient's mother and grandmother who were phenotypically normal carried the same unbalanced translocation. The 17q11.2 microdeletion had arisen de novo. Array comparative genomic hybridization (CGH) demonstrated gain of a 550-kb segment from 7qter and loss of 2.5 Mb from 17q11.2 (an atypical NF1 microdeletion). We conclude that the patient's phenotype is caused by the atypical NF1 deletion, whereas 7q36.3 trisomy represents a subtelomeric copy number variation without phenotypic consequences. To our knowledge this is the first report that a duplication of the subtelomeric region of chromosome 7q containing functional genes (FAM62B, WDR60, and VIPR2) can be tolerated without phenotypic consequences. The 17q11.2 microdeletion (containing nine more genes than the common NF1 microdeletions) and the 7qter duplication were not accompanied by unexpected clinical features. Most likely the 7qter trisomy and the 17q11.2 microdeletion coincide by chance in our patient.

[Obesity surgery in patients suffering from monogenetic adipositas]

Surgical treatment of patients suffering from monogenetic forms of morbid obesity is considered to be the poorest investigated theme in bariatric surgery. This review article presents aspects of genetic disorders in morbid obesity as well as some aspects of surgical treatment in patients with monogenetic forms of morbid obesity (Prader-Willi-Syndrome). Gastric restrictive procedures such as vertical banded gastroplasty or adjustable gastric banding as well as malabsorptive and mix procedures such as biliopancreatic diversion or Roux-en-Y gastric bypass are used for treatment, similar to polygenetic forms of morbid obesity. Until to now there is no evidence-based data because of the small number of published cases. Decisions about the indication to operation and about the choice of surgical procedures are based on the empiric fundament. It is to suggest that the use of growth hormones in patients with monogenetic forms of morbid obesity could positively influence the results of bariatric surgery in these patients.

Conserved synteny of mammalian imprinted genes in chicken, frog, and fish genomes

Conservation of synteny of mammalian imprinted genes between chicken and human suggested that highly conserved gene clusters were selected long before these genes were recruited for genomic imprinting in mammals. Here we have applied in silico mapping of orthologous genes in pipid frog, zebrafish, spotted green and Japanese pufferfish to show considerable conservation of synteny in lower vertebrates. More than 400 million years ago in a common ancestor of teleost fish and tetrapods, 'preimprinted' chromosome regions homologous to human 6q25, 7q21, 7q32, 11p15, and 15q11-->q12 already contained most present-day mammalian imprinted genes. Interestingly, some imprinted gene orthologues which are isolated from imprinted clusters in mouse and human could be linked to preimprinted regions in lower vertebrates, indicating that separation occurred during mammalian evolution. On the contrary, newly arisen genes by segmental duplication in the mammalian lineage, i.e. SNRPN and FRAT3, were transposed or translocated to imprinted clusters and recruited for parent-specific activity. By analysis of currently available sequences of non-mammalian vertebrates, the imprinted gene clusters homologous to human chromosomes 14q32 and 19q12 are only poorly conserved in chicken, frog, and fish and, therefore, may not have evolved from ancestral preimprinted gene arrays. Evidently, evolution of imprinted gene clusters is an ongoing and dynamic process in mammals. In general, imprinted gene orthologues do not show a higher degree of synteny conservation in vertebrates than non-imprinted genes interspersed with or adjacent to an imprinted cluster.

Deficient membrane integration of the novel p.N14D-GJB2 mutant associated with non-syndromic hearing impairment

Mutations in GJB2, the gene encoding for the Gap Junction protein Connexin 26 (Cx26), have been established as the major cause of hereditary, non-syndromic hearing impairment (HI). We report here the identification of a novel point mutation in GJB2, c.40A>G [p.N14D], detected in compound heterozygosity with the c.35delG mutation in two brothers with moderate non-syndromic sensorineural HI. The mother who carried one wildtype and a p.N14D allele displayed normal hearing. The mutation leads to substitution of the neutral amino acid asparagine (N) by the negatively charged aspartic acid (D) at amino acid number 14, a position that is conserved among Cx26 of different organisms and among many other connexin isoforms. To investigate the impact of this mutation on protein function, Cx26 activity was measured by depolarization activated hemichannel conductance in non-coupled Xenopus laevis oocytes. Oocytes injected with the p.N14D mutant cRNA showed strongly reduced currents compared to wildtype. Coinjection of wildtype and mutant cRNA at equimolar levels restored the conductive properties supporting the recessive character of this mutation. Total Cx26 protein expression and cell surface abundance examined by western blotting and by quantitative immunoassays revealed that the hemichannel was properly synthesized but not integrated into the plasma membrane. In this study we have shown that the GJB2 mutation p.N14D is associated with recessively inherited HI and exhibits a defective phenotype due to diminished expression at the cell surface.

Disruption of TCBA1 associated with a de novo t(1;6)(q32.2;q22.3) presenting in a child with developmental delay and recurrent infections

A boy with developmental delay, particularly of speech, a distinct face, antineutrophil cytoplasmic antibodies, and recurrent infections was found to have an apparently balanced de novo t(1;6)(q32.3;q22.3) translocation. Fluorescent in situ hybridisation with BAC/PAC clones and long range polymerase chain reaction products assessed in the human genome sequence localised the chromosome 1 breakpoint to a 9.8 kb segment within a hypothetical gene, LOC388735, and the chromosome 6 breakpoint to a 12.8 kb segment in intron 4 of the T-cell lymphoma breakpoint-associated target 1 (TCBA1) gene. Disruption and/or formation of TCBA1 fusion genes in T cell lymphoma and leukaemia cell lines suggests a role for this gene in tumorigenesis. The isolated mouse Tcba1 gene shows 91% amino acid sequence similarity with human TCBA1. It is expressed in fetal and adult brain and with lower levels in liver and testis. The human gene has been reported to be expressed exclusively in brain and thymus. Reduced TCBA1 expression in brain and thymus may explain at least some of the symptoms in this patient. It is concluded that germline alterations of the TCBA1 gene are associated with developmental delay and typical physical features.

Divergent genetic and epigenetic post-zygotic isolation mechanisms in Mus and Peromyscus

Interspecific hybridization in the rodent genera Peromyscus and Mus results in abnormal placentation. In the Peromyscus interspecies hybrids, abnormal allelic interaction between an X-linked locus and the imprinted paternally expressed Peg3 locus was shown to cause the placental defects. In addition, loss-of-imprinting (LOI) of Peg3 was positively correlated with increased placental size. As in extreme cases this placental dysplasia constitutes a post-zygotic barrier against interspecies hybridization, this finding was the first direct proof that imprinted genes may be important in speciation and thus in evolution. In the Mus interspecies hybrids, a strong role of an X-linked locus in placental dysplasia has also been detected. However, here we show by backcross and allele specific expression analyses that neither LOI of Peg3 nor abnormal interactions between Peg3 and an X-linked locus are involved in generating placental dysplasia in Mus hybrids, although the placental phenotypes observed in the two genera seem to be identical. In contrast to this, another dysgenesis effect common to Peromyscus and Mus hybrids, altered foetal growth, is caused at least in part by the same X-chromosomal regions in both genera. These findings first underline the strong involvement of the X-chromosome in the genetics of speciation. Secondly, they indicate that disruption of epigenetic states, such as LOI, at specific loci may be involved in hybrid dysgenesis effects in one group, but not in another. Thus, we conclude that even in closely related groups divergent molecular mechanisms may be involved in the production of phenotypically similar post-zygotic barriers against hybridization.

Genetic and genomic approaches to study placental development

Recent technological advances in genetic manipulation and expression profiling offer excellent opportunities to elucidate the molecular mechanisms controlling developmental processes during embryogenesis. Thus, this revolution also strongly benefits studies of the molecular genetics of placental development. Here we review the findings of several expression profiling analyses in extraembryonic tissues and assess how this work can contribute to the identification of essential components governing placental development. We further discuss the relevance of these components in the context of genetic manipulation experiments. In conclusion, the intelligent combination of genetic and genomic approaches will substantially accelerate the progress in identifying the key molecular pathways of placental development.

TGF alpha transgenic mice. A model of pancreatic cancer development

Pancreatic cancer is a devastating disease with a fatal prognosis due to late diagnosis and resistance to radiation and chemotherapy. The average survival after diagnosis is still 3 to 8 months. In the last few years genetic alterations in cancer-causing genes have been identified in tumors and putative premalignant lesions using microdissection techniques. However, the functional consequence of these genetic alterations for pancreatic growth and differentiation is unknown. TGF alpha overexpressed in the pancreas causes the development of tubular structures and fibrosis. Mice older than one year develop ductal pancreatic cancer. Crossbreeding these mice with p53 knockout mice dramatically accelerated tumor development. Moreover, tumors developing in these mice show frequently biallelic deletion of the Ink4a locus or LOH of SMAD4. These mice represent the first model of pancreatic adenocarcinomas with genetic alterations as well as growth characteristics similar to the human disease.

A high density of X-linked genes for general cognitive ability: a run-away process shaping human evolution?

The incidence of mental disability is 30% higher in males than in females. We have examined entries in the OMIM database that are associated with mental disability and for several other common defects. Our findings indicate that compared with the autosomes, the X chromosome contains a significantly higher number of genes that, when mutated, cause mental impairment. We propose that these genes are involved in the development of cognitive abilities and thus exert a large X-chromosome effect on general intelligence in humans. We discuss these conclusions with regard to the conservation of the vertebrate X-chromosomal linkage group and to human evolution.

Do the constraints of human speciation cause expression of the same set of genes in brain, testis, and placenta?

Evolution appears to be especially rapid during speciation, and the genes involved in speciation should be evident in species such as humans that have recently speciated or are presently in the process of speciation. Haldane's rule is that when one sex is sterile or inviable in interspecific F(1) hybrids, it is usually the heterogametic sex. For mammals, this implicates genes on the X chromosome as those particularly responsible for speciation. A preponderance of sex- and reproduction-related genes on the X chromosome has been shown repeatedly, but also mental retardation genes are more frequent on the X chromosome. We argue that brain, testis, and placenta are those organs most responsible for human speciation. Furthermore, the high degree of complexity of the vertebrate genome demands coordinate evolution of new characters. This coordination is best attained when the same set of genes is redeployed for these new characters in the brain, testis, and placenta.

Genetic and developmental analysis of X-inactivation in interspecific hybrid mice suggests a role for the Y chromosome in placental dysplasia

It has been shown previously that abnormal placental growth, i.e., hyper- and hypoplasia, occurs in crosses and backcrosses between different mouse (Mus) species. A locus that contributes to this abnormal development has been mapped to the X chromosome. Unexpectedly, an influence of fetal sex on placental development has been observed, in that placentas attached to male fetuses tended to exhibit a more pronounced phenotype than placentas attached to females. Here, we have analyzed this sex dependence in more detail. Our results show that differences between male and female placental weights are characteristic of interspecific matings and are not observed in intraspecific Mus musculus matings. The effect is retained in congenic lines that contain differing lengths of M. spretus-derived X chromosome. Expression of the X-linked gene Pgk1 from the maternal allele only and lack of overall activity of two paternally inherited X-linked transgenes indicate that reactivation or lack of inactivation of the paternal X chromosome in trophoblasts of interspecific hybrids is not a frequent occurrence. Thus, the difference between male and female placentas seems not to be caused by faulty preferential X-inactivation. Therefore, these data suggest that the sex difference of placental weights in interspecific hybrids is caused by interactions with the Y chromosome.

Expression pattern of the peripheral myelin protein 22kDa (PMP22) in neural and non-neural tissue types of adult wildtype and Trembler mice--a comparative study

The Trembler mouse was the first animal model for Charcot-Marie-Tooth disease type 1 (CMT1), one of the most frequent inherited peripheral neuropathies in man. In Trembler mouse a Gly150Asp amino acid exchange in the peripheral myelin protein 22kDa (PMP22) gene was identified as causative reason for this hypertrophic neuropathy. For most of the CMT patients suffering from the subtype 1A a duplication of the PMP22 gene is found (gene dosage effect); but several PMP22 point mutations, such as that determining the TremblerJ mouse, have also been described. Since PMP22 is expressed in neural, as well as in non-neural tissues, the expression pattern of PMP22 in different tissues seems to be of highest interest for a better understanding of the hypothesized dual function of this protein. We studied different wildtype (wt) and Trembler (Tr) mouse tissues for PMP22 expression by means of radioactive in situ hybridization (RISH) and immunohistochemistry. A PMP22 expression was found in some of the non-neural and in all neural tissue types studied. Our in situ study clearly demonstrated, that PMP22 mRNA expression in non-neural tissues is not due to peripheral innervation. In non-neural tissues no difference in the expression pattern or intensity between wt and Tr mice was detectable, whereas PMP22 expression in the peripheral nervous system (PNS) of the Tr mouse was extremely reduced. Immunohistochemical analysis of sciatic nerve sections revealed the same maldistribution of PMP22 in Tr mice as in sural nerve biopsies of CMT1 patients.

Lack of correlation between placenta and offspring size in mouse interspecific crosses

The placenta plays a pivotal role in fetal growth control and is considered a major site of genetic conflict between maternal and paternal genomes within the conceptus and, in addition, the genome of the mother. Accordingly, placental development is a strictly controlled process, and both placental and fetal weights do not vary much in intraspecific crosses of laboratory mice (Mus musculus). In mouse interspecific crosses and backcrosses [(M. musculus x M. spretus) x M. musculus], tremendous variation of placental, but not of fetal weight was observed. We have studied trophoblast cell type distribution and differentiation, and their effect on the associated placentas and fetuses in such backcrosses. Differentiation of spongious trophoblast, but not size of materno-fetal interface, correlated with fetal weight. Giant fetuses were observed only if less than one third of the spongiotrophoblast was formed by glycogen cells. Thus, placental efficiency was inversely related to the amount of glycogen cells. This influence of a trophoblast-derived cell type on fetal growth was not anticipated. We conclude that: (1) glycogen cells are able to negatively modulate fetal growth by an as yet unidentified mechanism; (2) correlation between fetal and placental weights is weak or absent in interspecific hybrids; (3) impaired control over placental and embryonic development in hybrids may contribute to post-mating isolation of species.

Genetic dissection of X-linked interspecific hybrid placental dysplasia in congenic mouse strains

Interspecific hybridization in the genus Mus results in male sterility and X-linked placental dysplasia. We have generated several congenic laboratory mouse lines (Mus musculus) in which different parts of the maternal X chromosome were derived from M. spretus. A strict positive correlation between placental weight and length of the M. spretus-derived part of the X chromosome was shown. Detailed analysis was carried out with one congenic strain that retained a M. spretus interval between 12.0 and 30.74 cM. This strain consistently produced hyperplastic placentas that exhibited an average weight increase of 180% over the weight of control placentas. In derived subcongenic strains, however, increased placental weight could no longer be observed. Morphometric analysis of these placentas revealed persistence of abnormal morphology. Fully developed placental hyperplasia could be reconstituted by recombination of proximal and central M. spretus intervals with an intervening M. musculus region. These results may suggest that placental dysplasia of interspecific mouse hybrids is caused by multiple loci clustered on the X chromosome that act synergistically. Alternatively, it is possible that changes in chromatin structure in interspecific hybrids that influence gene expression are dependent on the length of the alien chromosome.

Characterization of the mouse Src homology 3 domain gene Sh3d2c on Chr 7 demonstrates coexpression with huntingtin in the brain and identifies the processed pseudogene Sh3d2c-ps1 on Chr 2

Formation of intracellular protein complexes is often mediated by Src homology 3 domain-containing proteins interacting with proline-rich target sequences on other proteins. The Sh3d2c gene or its rat/human orthologs have been implicated in synaptic vesicle recycling due to interaction with dynamin I and synaptojanin in nerve terminals. In a yeast two-hybrid system, association with a huntingtin fragment containing an elongated stretch of polyglutamines was observed recently. By genetic mapping and fluorescence in situ hybridization we demonstrate the localization of Sh3d2c on mouse chromosome 7. A processed pseudogene of Sh3d2c, Sh3d2c-ps1, was identified and mapped to mouse chromosome 2. Using RNA in situ hybridization, we show that Sh3d2c is transcribed in various regions of the brain. The striatum, hippocampus, cortex, basal hypothalamus, brain stem, and cerebellum are the most prominent sites of expression. Because huntingtin and Sh3d2c are coexpressed in most regions of the brain, it can be speculated that there is a link between the association of huntingtin/Sh3d2c and the pathogenesis of Huntington disease.

An evolutionarily conserved gene on human chromosome 5q33-q34, UBH1, encodes a novel deubiquitinating enzyme

While cloning breakpoint sequences of a leukemia patient exhibiting a t(5; 14) translocation, we identified a pseudogenic variant of a novel multigene family in proximity to the breakpoint. Chromosomal in situ hybridization suggested that the gene family is clustered on human chromosome 5q33-q34. The gene family is evolutionarily conserved. Northern blot analysis of mouse tissues revealed low-level expression of a functional member of this gene family in almost all samples. Marked levels of transcripts were detected by in situ hybridization in the retina, the olfactory epithelium, the peripheral neuronal ganglia, and distinct areas of the gut. The predicted protein displays striking similarity to a hypothetical protein of Caenorhabditis elegans (R10E11.3.) and to two yeast deubiquitinating enzymes, Ubp9 and Ubp13, albeit to a lesser extent. We expressed the putative coding region of the human gene in Escherichia coli and demonstrated that it indeed bears deubiquitinating activity based on its ability to cleave ubiquitin from a ubiquitin-beta-galactosidase fusion protein. This new deubiquitinating enzyme has been named UBH1, for ubiquitin hydrolyzing enzyme 1.

Paternal transmission of X-linked placental dysplasia in mouse interspecific hybrids

It has previously been shown that abnormal placental development, i.e., hyper- and hypoplasia, occurs in crosses and backcrosses between different mouse (Mus) species. These defects are caused mainly by abnormal growth of the spongiotrophoblast. The precise genetic basis for these placental malformations has not been determined. However, a locus that contributes to the abnormal development (Ihpd: interspecific hybrid placental dysplasia) has been mapped to the X chromosome. The X-chromosomal location of Ihpd and its site of action, that is the spongiotrophoblast, mean that normally only the maternally inherited Ihpd locus is active even in female fetuses. However, by making use of the X-chromosomal inversion In(X)IH, we have produced interspecific hybrid Xp0, in which the active X chromosome was inherited from Mus macedonicus males. In contrast to XX female and XY male conceptuses from this cross, which have hypoplastic placentas, the Xp0 female conceptuses have hyperplastic placentas. This finding supports the view that it is expression of the M. macedonicus Ihpd locus in the spongiotrophoblast that leads to hyperplasia due to an abnormal interaction with M. musculus autosomal loci.