Predominant maternal expression of the mouse Atp10c in hippocampus and olfactory bulb

The human chromosome 15q11-q13 region is one of the most intriguing imprinted domains, and the abnormalities inherited are associated with neurological disorders including Prader-Willi syndrome (PWS), Angelman syndrome (AS) and autism. Recently we have identified a novel maternally expressed gene, ATP10C, that encodes a putative aminophospholipid translocase within this critical region, 200 kb distal to UBE3A in an imprinted domain on human chromosome 15. ATP10C, with UBE3A, displayed tissue-specific imprinting with predominant expression of the maternal allele in the brain. In this study, we demonstrated that the mouse homologue, Atp10c/pfatp, showed tissue-specific maternal expression in the hippocampus and olfactory bulb, which overlapped the region of imprinted Ube3a expression. These data suggest that the imprinted transcript of Atp10c in the specific region of CNS may be associated with neurological disorders including AS and autism.

Calcr, a brain-specific imprinted mouse calcitonin receptor gene in the imprinted cluster of the proximal region of chromosome 6

Expressed sequence tags (ESTs) in the human chromosome 7q21-q31 region were recently used to screen for allelic expression bias in monochromosomal hybrids retaining a paternal or maternal human chromosome 7. Six candidate imprinted genes were identified. In this study, we investigated parent-of-origin-specific expression profiles of their mouse homologues in the proximal region of chromosome 6. An imprinting analysis, using F1 mice from reciprocal crosses between the B6 and JF strains, demonstrated that the mouse calcitonin receptor gene ( Calcr) was expressed preferentially from the maternal allele in brain, whereas no allelic bias was detected in other tissues. Our results indicate that Calcr is imprinted in a tissue-specific manner, with a predominant expression from the maternal allele in the brain.

A new imprinted cluster on the human chromosome 7q21-q31, identified by human-mouse monochromosomal hybrids

We have previously established a series of human monochromosomal hybrids containing a single human chromosome of defined parental origin as an in vitro resource for the investigation of human imprinted loci. Using the hybrids with a paternal or maternal human chromosome 7, we determined the allelic expression profiles of 76 ESTs mapped to the human chromosome 7q21-q31. Seven genes/transcripts, including PEG10 which has previously been reported to be imprinted, showed parent-of-origin-specific expression in monochromosomal hybrids. One of the 6 candidate genes/transcripts, i.e., DLX5 was confirmed to be imprinted in normal human lymphoblasts and brain tissues by a polymorphic analysis. Thus, an imprinted domain has been newly defined in the region of human chromosome 7q21-q31 using human-mouse monochromosomal hybrids.

Discovery of imprinted transcripts in the mouse transcriptome using large-scale expression profiling

Candidate imprinted transcriptional units in the mouse genome were identified systematically from 27,663 FANTOM2 full-length mouse cDNA clones by expression profiling. Large-scale cDNA microarrays were used to detect differential expression dependent upon chromosomal parent of origin by comparing the mRNA levels in the total tissue of 9.5 dpc parthenogenote and androgenote mouse embryos. Of the FANTOM2 transcripts, 2114 were identified as candidates on the basis of the array data. Of these, 39 mapped to known imprinted regions of the mouse genome, 56 were considered as nonprotein-coding RNAs, and 159 were natural antisense transcripts. The imprinted expression of two transcripts located in the mouse chromosomal region syntenic to the human Prader-Willi syndrome region was confirmed experimentally. We further mapped all candidate imprinted transcripts to the mouse and human genome and were shown in correlation with the imprinting disease loci. These data provide a major resource for understanding the role of imprinting in mammalian inherited traits.

Successful ex vivo normothermic liver perfusion with purely artificial products using artificial blood

We tried to make an ex vivo functioning liver with an artificial perfusate that consisted of artificial blood in the pig liver. A liver graft from a female pig weighing 20 kg was harvested in the usual manner. The perfusion solution consisted of artificial blood, L-15 medium, distilled water, bovine serum albumin, NaHCO3, NaOH, KCl, human regular insulin, 50% glucose solution, and dexamethasone. The isolated liver was perfused with this oxygenated perfusate through the portal vein at a rate of 300 ml/min for 9 hours. Seven livers were perfused for 9 hours in this system. Five of the livers showed mean oxygen consumption of over 8 ml-O2/min during perfusion. Histological findings showed that the hepatic architecture was almost completely preserved and numerous hepatocytes exhibited PAS-positive cytoplasmic glycogen deposits in these livers. These observations indicate that we have succeeded in developing an ex vivo functioning liver with an artificial perfusate employing artificial blood.

Identification and characterization of an imprinted antisense RNA (MESTIT1) in the human MEST locus on chromosome 7q32

Imprinted gene(s) on human chromosome 7 are thought to be involved in Russell-Silver syndrome (RSS), based on the fact that approximately 10% of patients have maternal uniparental disomy of chromosome 7. However, involvement of the known imprinted genes (GRB10 at 7p12, PEG10 at 7q21.3 and MEST at 7q32) in RSS has yet to be established. To screen for new imprinted genes, we are initially using somatic cell hybrids containing a paternal or maternal human chromosome 7. Transcripts located between D7S530 and D7S649 (a 1.5 Mb interval encompassing MEST ) were subjected to RT-PCR analysis using somatic cell hybrids. One transcript named MESTIT1 (for MEST intronic transcript 1) reproducibly showed paternal-specific expression. Upon further analysis, we found MESTIT1 to be (1) paternally (and not maternally) expressed in all fetal tissues and fibroblasts examined, (2) to be located in an intron of one of the two isoforms of MEST but transcribed in the opposite direction, (3) to be composed of at least two exons without any significant open reading frame, and (4) to exist as a 4.2 kb transcript in many fetal and adult tissues. We could also identify two isoforms of the mouse Mest gene as observed in humans, but it is still unknown if a murine ortholog of MESTIT1 exists. We also examined the imprinting status of MEST isoforms as a first step in assessing whether MESTIT1 might influence the allelic expression pattern of the sense transcript. MEST isoform 1 was determined to be exclusively expressed from the paternal allele in all fetal tissues and cell lines examined, whereas MEST isoform 2 was only preferentially expressed from the paternal allele in a tissue/cell-type-specific manner. Our results suggest that MESTIT1 is a paternally expressed non-coding RNA that may be involved in the regulation of MEST expression during development. MESTIT1 (also known as PEG1-AS) is now the third independent transcript (with MEST and COPG2IT1) identified at human chromosome 7q32 demonstrating paternal chromosome-specific expression.

Asb4, Ata3, and Dcn are novel imprinted genes identified by high-throughput screening using RIKEN cDNA microarray

Genes differentially expressed between parthenogenetic and androgenetic embryos are candidates for the identification of imprinted genes, which are expressed specifically from the maternal or paternal allele. To search for genes differentially expressed between parthenogenetic and androgenetic embryos, we used the RIKEN full-length enriched mouse cDNA microarray. The 25 candidates obtained included 8 known imprinted genes (such as IgfII, Snrpn, and Neuronatin) and 3 new ones--Asb4 (ankyrin repeat and SOCS box-containing protein 4), Ata3 (amino acid transport system A3), and Decorin--which were confirmed by using normal diploid embryos from the reciprocal F1 crosses of B6 and JF1 mice. The 25 candidates also included genes that showed no imprinting-associated expression in normal diploid embryos. We describe a feasible high-throughput method of screening for novel imprinted genes by using the RIKEN cDNA microarray.

Molecular genetic studies of human chromosome 7 in Russell-Silver syndrome

Russell-Silver syndrome (RSS) is a form of congenital short stature characterized by severe growth retardation and variable dysmorphic features. In some RSS individuals, alterations in imprinted genes may be involved because approximately 7% of sporadic patients have been observed to have maternal uniparental disomy (mUPD) of chromosome 7. RSS patients with structural abnormalities of chromosome 7 have also been described. In these individuals the chromosome rearrangement could disrupt the balance of imprinted genes, contribute to a recessive form of RSS, or lead to haploinsufficiency of a crucial developmental gene product. Because the mechanism and molecular defects on chromosome 7 causing RSS are still unknown, we tested our collection of 77 RSS families for mUPD7 and were able to identify three new cases. We also characterized two RSS patients with de novo cytogenetic abnormalities involving the short arm of chromosome 7. One had a partial duplication [46, XX, dup(7)(p12 p14)] and the second contained a paracentric inversion [46, XY, inv(7)(p14 p21)]. Fluorescence in situ hybridization (FISH) mapping revealed that the breakpoints on 7p14 were localized to the same novel gene, C7orf10, which encompasses >700 kb of DNA. We also identified other transcription units from this immediate region, but all seem to be biallelically expressed when using a somatic cell hybrid assay.

Elderly Japanese emigrants to Brazil before World War II: I. Clinical profiles based on specific historical background

OBJECTIVE

To research the demographic and clinical profiles of elderly Japanese emigrants, who arrived in Brazil before World War II, in order to give them appropriate psychogeriatric care.

DESIGN

Elderly Japanese immigrants aged 65 years and over, belonging to the Miyagi Association in the São Paulo Metropolitan Area, were targeted. They emigrated from Miyagi Prefecture to Brazil and are now living in the area. We were able to interview 166 respondents. All data were gathered using standardized interview methods covering (a) free interview about the immigration history, (b) demographics, and (c) physical status.

RESULTS

Through the free interview, we found their immigration histories, which affected their clinical profiles. The mean age and educational level were 77.5 years and 6.3 years, respectively. Sixty per cent of them immigrated when they were younger than 14. Ninety-four per cent of them still keep Japanese nationality. Fifty-seven per cent of them usually use Japanese, while 10% of them use Portuguese. Although their emigration histories were hard, 76% of them perceived their health as being excellent or relatively good. The percentages of subjects with histories of disease were hypertension, 52.5%; cardiac disease, 20.8%; diabetes mellitus, 24.2%; and hyperlipidemia, 25.0%, which were affected by the Brazilian environment.

CONCLUSION

The elderly Japanese who emigrated to Brazil before World War II have a unique historical and demographic background. Their clinical profiles cannot be fully understood without knowing their histories. They definitely need high quality international psychogeriatric care.

Elderly Japanese emigrants to Brazil before World War II: II. Prevalence of senile dementia

BACKGROUND

We previously showed the prevalence of dementia in the town of Tajiri (Miyagi Prefecture, Japan), and found it to be 8.0%. The first population-based study on dementia in Brazil (Catanduva) disclosed the prevalence as being 7.1%. To evaluate the effects of environment on development of dementia, elderly Japanese immigrants living in Brazil were examined. Brazil is the country with the largest number of Japanese immigrants.

METHODS

All immigrants aged 65 years and over from Miyagi Prefecture, living in the four cities of the São Paulo Metropolitan area were targeted (n = 192). We were able to examine 166 subjects (86.5%). The diagnosis of dementia was based on the DSM-IV with the severity assessed by the CDR (clinical dementia rating) scales. The cognitive ability screening instrument (CASI) was used for neuropsychological assessment.

RESULTS

Thirteen subjects were diagnosed with dementia, CDR 1-3, the prevalence being 7.8%. Older subjects suffered more from dementia, and, paradoxically, the more highly educated subjects also suffered more. All the CASI items, except for long-term memory and visual construction, significantly deteriorated in the CDR 0.5 group compared with the CDR 0 group.

COMMENTS

The prevalence of dementia was not thought to be affected by environmental factors. A paradoxically higher rate of dementia in the more educated subjects was probably due to the historical problems of the immigrants. Intact CASI item long-term memory in the CDR 0.5 group indicated that suspected dementia patients could maintain this function. This is the first epidemiological study on dementia in elderly Japanese immigrants in Brazil.

Epigenetic heterogeneity at imprinted loci in normal populations

Genomic imprinting is the phenomenon by which the two alleles of certain genes are differentially expressed according to their parental origin. Extensive analysis of allelic expression at multiple imprinted loci in a normal population has not performed so far. In the present study, we examined the allelic expression pattern of three imprinted genes in a panel of 262 Japanese normal individuals. We observed differences in the extent of maintenance of allele-specific expression of the three genes. The allelic expression of small nuclear ribonucleoprotein N (SNRPN) was stringently regulated while that of multimembrane-spanning polyspecific transporter-like gene 1 (IMPT1) showed a large degree of variation. Significant biallelic expression of insulin-like growth factor II (IGF2) was observed in about 10% of normal individuals. Our findings add to the accumulating evidence for variable allelic expression at multiple loci in a normal human population. This epigenetic heterogeneity can be a stable trait and potentially influence individual phenotypes.

Loss of imprinting of long QT intronic transcript 1 in colorectal cancer

Loss of imprinting (LOI) of the insulin-like growth factor 2 (IGF2) and H19 genes on human chromosome 11 has been found not only in childhood tumors but also in common adult cancers including colorectal cancer. Recently, a transcript called LIT1 (long QT intronic transcript 1) has been identified within the KvLQT1 locus on chromosome 11. LIT1 is expressed preferentially from the paternal allele and is transcribed in most human tissues. LOI of LIT1 was found in a considerable number of Beckwith-Wiedemann syndrome (BWS) patients, suggesting that it is associated with the etiology of BWS. Since LOI of IGF2 was observed in association with overexpression of IGF2 in colorectal cancer in our previous study, we examined the status of genomic imprinting of LIT1 and H19 in comparison with IGF2 in colorectal cancer. We examined 44 surgically dissected colorectal cancer tissues. Ten of them represented informative cases for LIT1. None of these patients exhibited loss of heterozygosity (LOH) of LIT1, and LOI of LIT1 was observed in 4 of the 10 (40%) informative patients, but not in non-cancerous tissues. Neither LOH nor LOI of H19 was observed. LOI of IGF2 was observed in 4 of 18 (22%) informative patients. These results suggest that LOI of LIT1 is frequently observed in colorectal cancer and may be a useful marker for diagnosis of colorectal cancer.

A novel maternally expressed gene, ATP10C, encodes a putative aminophospholipid translocase associated with Angelman syndrome

Lack of a maternal contribution to the genome at the imprinted domain on proximal chromosome 15 causes Angelman syndrome (AS) associated with neurobehavioral anomalies that include severe mental retardation, ataxia and epilepsy. Although AS patients have infrequent mutations in the gene encoding an E6-AP ubiquitin ligase required for long-term synaptic potentiation (LTP), most cases are attributed to de novo maternal deletions of 15q11-q13. We report here that a novel maternally expressed gene, ATP10C, maps within the most common interval of deletion and that ATP10C expression is virtually absent from AS patients with imprinting mutations, as well as from patients with maternal deletions of 15q11-q13.

Large-scale evaluation of imprinting status in the Prader-Willi syndrome region: an imprinted direct repeat cluster resembling small nucleolar RNA genes

Loss of paternal gene expression at the imprinted domain on proximal human chromosome 15 causes Prader-Willi syndrome (PWS), a complex multiple-anomaly disorder involving variable mental retardation, hyperphasia leading to obesity and infantile hypotonia with failure to thrive. Although numerous paternally expressed transcripts have been identified that reside in the candidate region, the individual contributions to the development of PWS have not been firmly established. Recent studies of mouse models carrying a cytogenetic deletion suggest that paternal deficiency of the SNRPN-IPW interval is critical for perinatal lethality of potential relevance to PWS. Here we determined the allelic expression profiles of a total of 118 cDNA clones using monochromosomal hybrids retaining either a paternal or maternal human chromosome 15. Our results demonstrated a preponderance of unusual transcripts lacking protein-coding potential that were expressed exclusively from the paternal copy of the critical interval. This interval was also found to encompass a large direct repeat (DR) cluster displaying a potentially active chromatin conformation of paternal origin, as suggested by enhanced sensitivity to nuclease digestion. Database searches revealed an unexpected organization of tandemly repeated consensus elements, all of which possessed well-defined box C and D sequences characteristic of small nucleolar RNAs (snoRNAs). Southern blot analysis further demonstrated a considerable degree of phylogenetic conservation of the DR locus in the genomes of all mammalian species tested, but not in chicken, Xenopus and Drosophila. These findings imply a potential direct contribution of the DR locus, representing a cluster of multiple snoRNA genes, to certain phenotypic features of PWS.

Targeted disruption of the human LIT1 locus defines a putative imprinting control element playing an essential role in Beckwith-Wiedemann syndrome

Human chromosome 11p15.5 harbors an intriguing imprinted gene cluster of 1 Mb. This imprinted domain is implicated in a wide variety of malignancies and Beckwith-Wiedemann syndrome (BWS). Recently, several lines of evidence have suggested that the BWS-associated imprinting cluster consists of separate chromosomal domains. We have previously identified LIT1, a paternally expressed antisense RNA within the KvLQT1 locus through a positional screening approach using human monochromosomal hybrids. KvLQT1 encompasses the translocation breakpoint cluster in BWS and patients exhibit frequent loss of maternal methylation at the LIT1 CpG island, implying a regulatory role for the LIT1 locus in coordinate control of the imprinting cluster. Here we generated modified human chromosomes carrying a targeted deletion of the LIT1 CpG island using recombination-proficient chicken DT40 cells. Consistent with the prediction, this mutation abolished LIT1 expression on the paternal chromosome, accompanied by activation of the normally silent paternal alleles of multiple imprinted loci at the centromeric domain including KvLQT1 and p57(KIP2). The deletion had no effect on imprinting of H19 located at the telomeric end of the cluster. Our findings demonstrate that the LIT1 CpG island can act as a negative regulator in cis for coordinate imprinting at the centromeric domain, thereby suggesting a role for the LIT1 locus in a BWS pathway leading to functional inactivation of p57(KIP2). Thus, the targeting and precise modification of human chromosomal alleles using the DT40 cell shuttle system can be used to define regulatory elements that confer long-range control of gene activity within chromosomal domains.

Changes in hepatic venous oxygen saturation in hepatic warm ischemia/reperfusion injury in pigs

To clarify the changes that occur in hepatic venous oxygen saturation (ShVO2) during hepatic ischemia/reperfusion (I/R) injury, we examined the relationship between ShVO2, hepatic tissue blood flow (HTBF), and portal vein pressure (PVP) in a warm I/R model using pig livers. Female pigs weighing 18-23 kg were subjected to warm I/R under extracorporeal circulation between the superior mesentric vein and the left jugular vein to avoid portal congestion. The warm ischemic times were 120 min (n = 4), 180 min (n = 14), and 240 min (n = 4). ShVO2, HTBF, and PVP were measured after reperfusion. The survival rates of the pigs 3 days after reperfusion were 100% in the 120-min group, 57% in the 180-min group, and 25% in the 240-min group. In the 180-min group, the ShVO2 was lower in the pigs that died than in those that survived. There was a significant correlation between ShVO2 and both PVP and HTBF after reperfusion. Histological examination revealed findings of severe I/R injury in pigs with a low ShVO2, and mild I/R injury in pigs with a stable ShVO2. These observations suggest that the changes in ShVO2 could reflect the degree of hepatic I/R injury, especially that related to microcirculatory disturbances occurring at the sinusoid levels.

LIT1, an imprinted antisense RNA in the human KvLQT1 locus identified by screening for differentially expressed transcripts using monochromosomal hybrids

Mammalian imprinted genes are frequently arranged in clusters on particular chromosomes. The imprinting cluster on human chromosome 11p15 is associated with Beckwith-Wiedemann syndrome (BWS) and a variety of human cancers. To clarify the genomic organization of the imprinted cluster, an extensive screen for differentially expressed transcripts in the 11p15 region was performed using monochromosomal hybrids with a paternal or maternal human chromosome 11. Here we describe an imprinted antisense transcript identified within the KvLQT1 locus, which is associated with multiple balanced chromosomal rearrangements in BWS and an additional breakpoint in embryonal rhabdoid tumors. The transcript, called LIT1 (long QT intronic transcript 1), was expressed preferentially from the paternal allele and produced in most human tissues. Methylation analysis revealed that an intronic CpG island was specifically methylated on the silent maternal allele and that four of 13 BWS patients showed complete loss of maternal methylation at the CpG island, suggesting that antisense regulation is involved in the development of human disease. In addition, we found that eight of eight Wilms' tumors exhibited normal imprinting of LIT1 and five of five tumors displayed normal differential methylation at the intronic CpG island. This contrasts with five of six tumors showing loss of imprinting of IGF2. We conclude that the imprinted gene domain at the KvLQT1 locus is discordantly regulated in cancer from the imprinted domain at the IGF2 locus. Thus, this positional approach using human monochromosomal hybrids could contribute to the efficient identification of imprinted loci in humans.

Mouse A9 cells containing single human chromosomes for analysis of genomic imprinting

To develop an systematic in vitro approach for the study of genomic imprinting, we generated a new library of human/mouse A9 monochromosomal hybrids. We used whole cell fusion and microcell-mediated chromosome transfer to generate A9 hybrids containing a single, intact, bsr-tagged human chromosome derived from primary fibroblasts. A9 hybrids were identified that contained either human chromosome 1, 2, 4, 5, 7, 8, 10, 11, 15, 18, 20, or X. The parental origin of these chromosomes was determined by polymorphic analysis using microsatellite markers, and matched hybrids containing maternal and paternal chromosomes were identified for chromosomes 5, 10, 11 and 15. The imprinted gene KVLQT1 on human chromosome 11p15.5 was expressed exclusively from the maternal chromosome in A9 hybrids, and the parental-origin-specific expression patterns of several other imprinted genes were also maintained. This library of human monochromosomal hybrids is a valuable resource for the mapping and cloning of human genes and is a novel in vitro system for the screening of imprinted genes and for their functional analysis.

Epigenetic reprogramming of the human H19 gene in mouse embryonic cells does not erase the primary parental imprint

BACKGROUND

Genomic imprinting in mammals is thought to result from epigenetic modifications to chromosomes during gametogenesis, which leads to differential allelic expression during development. There is a requirement for an appropriate experimental system to enable the analysis of the mechanisms of genomic imprinting during embryogenesis.

RESULTS

To develop a novel in vitro system for studying the molecular basis of genomic imprinting, we constructed mouse cell lines containing either a paternal or maternal human chromosome 11, by microcell-mediated chromosome transfer. Allele-specific expression and DNA methylation studies revealed that the imprinting status of the human H19 gene was maintained in mouse A9 mono-chromosomal hybrids. Each parental human chromosome was introduced independently into mouse near-diploid immortal fibroblasts (m5S) and two embryonal carcinoma (EC) cell lines (OTF9-63 and P19). The paternal allele of human H19 remained in a repressed state in m5S cells, but was de-repressed in both EC cells. The paternal H19 allele was demethylated extensively in OTF9-63 cells, whereas the only alteration in P19 hybrids was de novo methylation on both alleles in the 3' region. Following in vitro differentiation, the expressed paternal H19 allele was selectively repressed in differentiated derivatives of EC hybrids.

CONCLUSION

These results indicated that human imprint marks could function effectively in mouse cells, and that the imprinting process was epigenetically reprogrammed in embryonal carcinoma cells, without erasure of the primary imprint that marked the parental origin. Therefore, these mono-chromosomal hybrids could provide a valuable in vitro system to study the mechanisms involved in the regulation of imprinted gene expression.

Paternal expression of WT1 in human fibroblasts and lymphocytes

The Wilms' tumor suppressor gene ( WT1 ) was previously identified as being imprinted, with frequent maternal expression in human placentae and fetal brains. We examined the allele-specific expression of WT1 in cultured human fibroblasts from 15 individuals. Seven of 15 fibroblast lines were heterozygous for polymorphic alleles, and the expression patterns were variable, i.e., equal, unequal or monoallelic paternal expression in three, two and two cases, respectively. Exclusive paternal expression of WT1 was also shown in non-cultured peripheral lymphocytes from the latter two individuals. The allele-specific expression profiles of other imprinted genes, IGF2 and H19, on human chromosome 11 were constant and consistent with those in other tissues. Our unexpected observations of paternal or biallelic expression of WT1 in fibroblasts and lymphocytes, together with the previous findings of maternal or biallelic expression in placentae and brains, suggest that the allele-specific regulatory system of WT1 is unique and may be controlled by a putative tissue- and individual-specific modifier.