The human MAGEL2 gene and its mouse homologue are paternally expressed and mapped to the Prader-Willi region.

Prader-Willi syndrome (PWS) is a complex neurogenetic disorder. The phenotype is likely to be a contiguous gene syndrome involving genes which are paternally expressed only, located in the human 15q11-q13 region. Four mouse models of PWS have been reported but these do not definitively allow the delineation of the critical region and the associated genes involved in the aetiology of PWS. Moreover, targeted mutagenesis of mouse homologues of the human candidate PWS genes does not appear to result in any of the features of PWS. Therefore, the isolation of new genes in this region remains crucial for a better understanding of the molecular basis of PWS. In this manuscript, we report the characterization of MAGEL2 and its mouse homologue Magel2. These are located in the human 15q11-q13 and mouse 7C regions, in close proximity to NDN / Ndn. By northern blot analysis we did not detect any expression of MAGEL2 / Magel2 but by RT-PCR analysis, specific expression was detected in fetal and adult brain and in placenta. Both genes are intronless with tandem direct repeat sequences contained within a CpG island in the 5'-untranscribed region. The transcripts encode putative proteins that are homologous to the MAGE proteins and NDN. Moreover, MAGEL2 / Magel2 are expressed only from the paternal allele in brain, suggesting a potential role in the aetiology of PWS and its mouse model, respectively.

The mouse Necdin gene is expressed from the paternal allele only and lies in the 7C region of the mouse chromosome 7, a region of conserved synteny to the human Prader-Willi syndrome region.

Prader-Willi syndrome (PWS) is a neurogenetic disorder resulting from the loss of paternal expression of gene(s) localized in the 15q11-q12 region. A new human gene encoding a putative protein with high homology to the mouse NECDIN protein has recently been characterized and mapped to chromosome 15q11-q12. It is expressed from the paternal allele only, suggesting its potential involvement in PWS. We now report the localization of the mouse Necdin gene in a region of conserved synteny to the human PWS region. We demonstrate the paternal specific expression of Necdin in the mouse central nervous system, and show that parental alleles display a differential methylation profile in the coding region. Finally, fluorescence in situ hybridization analysis reveals an asynchronous pattern of replication at the Necdin locus. These results clearly demonstrate imprinting of the mouse Necdin gene. Mouse models will be powerful tools in the study of human PWS phenotype and imprinting mechanisms.

The human necdin gene, NDN, is maternally imprinted and located in the Prader-Willi syndrome chromosomal region.

Prader-Willi syndrome (PWS) is a neurogenetic disorder that results from the absence of a normal paternal contribution to the 15q11-13 region. The clinical manifestations of PWS are a transient severe hypotonia in the newborn period, with mental retardation, hypogonadism and obesity observed later in development. Five transcripts with exclusive expression from the paternal allele have been isolated, but none of these has been shown to be involved in PWS. In this study, we report the isolation and characterization of NDN, a new human imprinted gene. NDN is exclusively expressed from the paternal allele in the tissues analysed and is located in the PWS region. It encodes a putative protein homologous to the mouse brain-specific NECDIN protein, NDN; as in mouse, expression in brain is restricted to post-mitotic neurons. NDN displays several characteristics of an imprinted locus, including allelic DNA methylation and asynchronous DNA replication. A complete lack of NDN expression in PWS brain and fibroblasts indicates that the gene is expressed exclusively from the paternal allele in these tissues and suggests a possible role of this new gene in PWS.

Genes of the membrane-type matrix metalloproteinase (MT-MMP) gene family, MMP14, MMP15, and MMP16, localize to human chromosomes 14, 16, and 8, respectively.

The membrane-type matrix metalloproteinases (MT-MMPs) constitute a newly discovered family of four enzymes within the matrix metalloproteinase (MMP) superfamily. We have mapped the genes for MT1-MMP (MMP14), MT2-MMP (MMP15), and MT3-MMP (MMP16) using in situ hybridization to human metaphase chromosomes. In contrast to the genes for many MMPs that are clustered on chromosome 11, the genes MMP14, MMP15, and MMP16 all map to distinct chromosomes. MMP14 maps to human chromosome 14, MMP15 to human chromosome 16, and MMP16 to human chromosome 8.

Isolation and regional mapping of cDNAs expressed during early human development.

A cDNA sequencing project was initiated with the aim of isolating and mapping new genes expressed during early human development. A human embryo cDNA library was constructed, and a prescreening procedure was used to select cDNAs corresponding to poorly transcribed genes. Partial sequences were generated from one or both ends of 231 cDNA clones, and sequence comparison with genetic databases revealed that 28% were already annotated genes, 42% matched with partial sequences expressed sequence tags that had already been detected, 3% contained no insert, 5% were highly similar to sequences from other species, and 23% of the cDNAs appeared to be unknown in genetic databases. All new sequences were deposited in public genetic databases, and most of the corresponding cDNAs were regionally mapped on human chromosome bands using both fluorescence and radioactive in situ hybridization. Several cDNAs colocalized with critical regions of the genome regarding mapped disorders, thus providing candidate genes for human genetic diseases.

Human testis specifically expresses a homologue of the rodent T lymphocytes RT6 mRNA.

A human homologue of the rodent T cell mono ADP-ribosyl transferase RT6 mRNA was identified by a systematic analysis of human testis transcripts. This messenger encodes for a precursor protein of 367 aa (MW: 41.5 kDa) which exhibits a peptide signal, consensus domains for mono ADP-ribosyl transferase and a C-terminal part characteristic of glycophosphatidyl inositol anchored protein. This mRNA, transcribed from a gene localized in 4q13-q21, is not expressed in white blood cells but is specific for human testis in which it is likely to correspond to a new ADP-ribosyl transferase.

Clinical heterogeneity in 16 patients with inv dup 15 chromosome: cytogenetic and molecular studies, search for an imprinting effect.

We report on clinical, cytogenetic and molecular analyses of 16 patients with inv dup (15) chromosome. We define the content of the inv dup (15) markers, their meiotic origin and the methylation status of the chromosome region involved. Precise phenotype-karyotype-genotype correlations allowed the identification of five different types of marker and demonstrated that even when the molecular content of the inv dup (15) chromosome clearly contributes to the severity of the phenotype, it does not appear to be the only relevant factor. All the markers were of maternal origin with an identical methylation profile, and neither imprinting nor methylation can explain the phenotypic variability. We suggest that the degree of phenotypic severity may be correlated with the severity of epilepsy.

Chromosomal mapping of human adenylyl cyclase genes type III, type V and type VI.

Adenylyl cyclase activity plays a central role in the regulation of most cellular processes. At least eight different adenylyl cyclases have been identified, which are endowed with various and sometimes opposing regulatory properties. Recently we have localized the human genes encoding two of these adenylyl cyclases: the gene for type II adenylyl cyclase is located on chromosome 2 (sub-band 2p15.3), the gene for type VIII is located on chromosome 8 (sub-band 8q24.2). More recently the type I gene has been located on chromosome 7 (sub-band 7p12-7p13). Using in situ hybridization, we have now localized the genes for three other adenylyl cyclases: the type III gene has been localized on chromosome 2 in the sub-band 2p22-2p24, the type V gene on chromosome 3 at position 3q13.2-3q21, and the type VI gene on chromosome 12 at position 12q12-12q13. It therefore appears that all adenylyl cyclase genes, known at present are located on different chromosomes and thus are likely to be independently regulated.

Chromosomal localization of human RNA polymerase II subunit genes.

The eukaryotic DNA-dependent RNA polymerase II (or B) is composed of 10 to 14 polypeptides ranging from 220 to 10 kDa. To gain further insight into the molecular structure and function of these subunits, we have undertaken the molecular cloning of nucleotide sequences corresponding to the human enzyme. The cDNAs of five subunits (hRPB220, hRPB140, hRPB33, hRPB25, and hRPB14.5) have been isolated. Using in situ hybridization, we show that the genes of these subunits have distinct chromosomal locations (17p13, 4q12, 16q13-q21, 19p13.3, and 19q12, respectively). Thus, if assembly of active polymerase molecules requires coordinated expression from these independent genes, mechanisms that ensure tight coregulation of the corresponding promoters must exist.

The major peripheral myelin protein zero gene: structure and localization in the cluster of Fc gamma receptor genes on human chromosome 1q21.3-q23.

We have characterized the human gene encoding the major peripheral myelin protein zero (P0) and assigned it, by in situ hybridization, to the q21.3-q23 region of human chromosome 1. This region is known to contain a cluster of interspersed genes coding for the related human leukocyte receptors of the Fc portion of the immunoglobulin G (Fc gamma RI, II, III). This colocalization was refined by the finding of a yeast artificial chromosome (YAC) of the Centre d'Etude du Polymorphisme Humain (CEPH) library, hybridizing to the P0 and Fc gamma RIIA genes, demonstrating their physical linkage. These data may have important implications in demyelinating diseases studies like Charcot-Marie-Tooth disease type 1B (CMT1B).

Myelin/oligodendrocyte glycoprotein is a member of a subset of the immunoglobulin superfamily encoded within the major histocompatibility complex.

Myelin/oligodendrocyte glycoprotein (MOG) is found on the surface of myelinating oligodendrocytes and external lamellae of myelin sheaths in the central nervous system, and it is a target antigen in experimental autoimmune encephalomyelitis and multiple sclerosis. We have isolated bovine, mouse, and rat MOG cDNA clones and shown that the developmental pattern of MOG expression in the rat central nervous system coincides with the late stages of myelination. The amino-terminal, extracellular domain of MOG has characteristics of an immunoglobulin variable domain and is 46% and 41% identical with the amino terminus of bovine butyrophilin (expressed in the lactating mammary gland) and B-G antigens of the chicken major histocompatibility complex (MHC), respectively; these proteins thus form a subset of the immunoglobulin superfamily. The homology between MOG and B-G extends beyond their structure and genetic mapping to their ability to induce strong antibody responses and has implications for the role of MOG in pathological, autoimmune conditions. We colocalized the MOG and BT genes to the human MHC on chromosome 6p21.3-p22. The mouse MOG gene was mapped to the homologous band C of chromosome 17, within the M region of the mouse MHC.

In humans all U3 genes map to chromosome 17p12-->p11, but in mouse the U3A and U3B genes are located on different chromosomes.

U3 small nucleolar RNA, which participates in eukaryotic rRNA processing, is encoded by a small multigene family in mammals. In humans, the four to six gene copies code for an identical U3 RNA molecule; rodents, however, have two variant forms of these genes, U3A and U3B. We show that all U3 genes in humans map to a single chromosomal locus, 17p12-->-p11, which corresponds exactly to the region of mouse Chromosome 11 where the four U3B genes are clustered. By contrast, in mouse the unique U3A gene copy is not linked to the U3B gene cluster but maps to another chromosome (the B2-B4 region of Chromosome 10).

Different chromosomal localization of two adenylyl cyclase genes expressed in human brain.

Recently, we characterized a cDNA clone that encodes a human brain adenylyl cyclase (HBAC1). In the present study, we identified a second population of mRNA suspected to encode a new brain adenylyl cyclase (HBA C2). The amino acid sequence of HBA C2 displays significant homology with HBA C1 in the highly conserved adenylyl cyclase domain (250 aminio acids), found in the 3' cytoplasmic domain of all mammalian adenylyl cyclases. However, outside this domain, the homology is extremely low, suggesting that the corresponding mRNA originates from a different gene. We report here the first chromosomal localization of the adenylyl cyclase genes determined by in situ hybridization of human metaphase chromosomal spreads using human brain cDNA probes specific for each mRNA. The probe corresponding to HBA C1 exhibited a strong specific signal on chromosome 8q24, with a major peak in the band q24.2. In contrast, the HBA C2 probe hybridized to chromosome 5p15, with a major peak in the band p15.3. The two cDNAs hybridized at the two loci without any cross reactivity. Thus, in human brain, a heterogeneous population of adenylyl cyclase mRNAs is expressed, and the corresponding genes might be under the control of independent regulatory mechanisms.

The human pre-B-specific lambda-like cluster is located in the 22q11.2-22q12.3 region, distal to the IgC lambda locus.

The chromosomal location of the lambda-like gene cluster, a gene family selectively expressed in human pre-B cells, was analyzed by in situ hybridization with a probe specific for the lambda-like genes. This cluster mapped in the q11.2-q12.3 region of chromosome 22. The use of Burkitt lymphoma and myelogenous leukemia cell lines with translocations in the 22q11 region led to a refinement in the location according to the following order: cen----BCRL2, VpreB, IgV lambda 1----BCRL4, IgV lambda----IgC lambda----BCR----BCRL3, lambda-like----tel. Unlike those of the mouse system, the pre-B-specific genes VpreB and lambda-like do not belong to the same transcriptional unit.

Mouse ferritin H sequences map to chromosomes 3, 6, and 19.

Human and rodent genomes contain multiple copies of ferritin H and L subunit sequences, although it is not yet clear whether there is more than one expressed gene for either of these subunits. We have isolated a cDNA corresponding to mouse ferritin H subunit and observed that the mouse genome contains three to four H-related sequences. This cDNA was used to establish the genomic location of mouse ferritin H subunit genes by chromosomal in situ hybridization. Metaphase chromosomes of concanavalin A-stimulated lymphocytes from a WMP male mouse were examined by in situ hybridization with 3H-labeled cDNA and the chromosomes were identified by R banding (fluorochrome-photolysis-Giemsa method). The results indicate that mouse ferritin H-related sequences map at chromosomes 3, 6, and 19. Homology of synteny between human and mouse suggests that the sequence on mouse chromosome 19 corresponds to the structural H gene.

Assignment of the human interferon-alpha receptor gene to chromosome 21q22.1 by in situ hybridization.

The human interferon-alpha receptor gene (IFN AR) has been assigned to the long arm of human chromosome 21 (report of the committee on the genetic constitution of chromosomes 20 and 21; Ref 1). The present report confirms the assignment and refines the mapping to the 21q22.1 band, using a cDNA probe for the human IFN AR gene and in situ hybridization to metaphase chromosomes.