IgM is the first antibody to be produced in a humoral immune response and plays an important role in the primary stages of immunity. Here we describe a mouse Fc receptor, designated Fc alpha/microR, and its human homolog, that bind both IgM and IgA with intermediate or high affinity. Fc alpha/microR is constitutively expressed on the majority of B lymphocytes and macrophages. Cross-linking Fc alpha/microR expressed on a pro-B cell line Ba/F3 transfectant with soluble IgM or IgM-coated microparticles induced internalization of the receptor. Fc alpha/microR also mediated primary B lymphocyte endocytosis of IgM-coated Staphylococcus aureus. Thus, Fc alpha/microR is involved in the primary stages of the immune response to microbes.

We have recently cloned the mouse activity-dependent neuroprotective protein (ADNP). Here, we disclose the cloning of human ADNP (hADNP) from a fetal brain cDNA library. Comparative sequence analysis of these two ADNP orthologs indicated 90% identity at the mRNA level. Several single nucleotide polymorphic sites were noticed. The deduced protein structure contained nine zinc fingers, a proline-rich region, a nuclear bipartite localization signal, and a homeobox domain profile, suggesting a transcription factor function. Further comparative analysis identified an ADNP paralog (33% identity and 46% similarity), indicating that these genes belong to a novel protein family with a nine-zinc finger motif followed by a homeobox domain. The hADNP gene structure spans ϳ40 kilobases and includes five exons and four introns with alternative splicing of an untranslated second exon. The hADNP gene was mapped to chromosome 20q12-13.2, a region associated with aggressive tumor growth, frequently amplified in many neoplasias, including breast, bladder, ovarian, pancreatic, and colon cancers. hADNP mRNA is abundantly expressed in distinct normal tissues, and high expression levels were encountered in malignant cells. Down-regulation of ADNP by antisense oligodeoxynucleotides up-regulated the tumor suppressor p53 and reduced the viability of intestinal cancer cells by 90%. Thus, ADNP is implicated in maintaining cell survival, perhaps through modulation of p53.Mouse activity-dependent neuroprotective protein (mADNP), 1 a novel vasoactive intestinal peptide (VIP)-responsive gene, was recently cloned (1). The relative enrichment of mADNP transcripts in the cerebellum, cortex, hippocampus, medulla, and midbrain and the increases found in the presence of VIP, an established neuroprotective substance (2), implied a potential function in brain metabolism. Specifically, mADNP mRNA increased 2-3-fold in astroglial cells incubated for 3 h in the presence of nanomolar amounts of VIP (1). Another tissue containing increased mADNP transcripts is the mouse testis, a highly proliferative tissue, suggesting the involvement of ADNP in cell division.As deregulation of oncogenes has been associated with neurodegeneration (3), pathways that regulate neuronal survival may impinge upon cancer proliferation. VIP regulates both neuronal survival and cell division (2). A system whereby labeled VIP is suggested as a tumor marker has been proposed, localizing in vivo tumors of patients with gastrointestinal neuroendocrine cancers as well as pancreatic and colonic adenocarcinomas (4). Other studies have identified a very high incidence of VIP receptor binding in breast, ovarian, endometrial, prostate, bladder, lung, esophageal, colonic, and pancreatic tumors as well as in neuroendocrine and brain tumors (5). However, the VIP effect on cancer growth depends on the specific tumor and may be stimulatory (6, 7) or inhibitory (8). In view of the high incidence of tumors containing VIP receptors, a potential intervention in tumor growth may employ a gene downstr...

Transmembrane mucins are glycoproteins involved in barrier function in epithelial tissues. To identify novel transmembrane mucin genes, we performed a tblastn search of the GenBank EST data bases with a serine/ threonine-rich search string, and a rodent gene expressed in bone marrow was identified. We determined the cDNA sequence of the human orthologue of this gene, MUC13, which localizes to chromosome band 3q13.3 and generates 3.2-kilobase pair transcripts encoding a 512-amino acid protein comprised of an N-terminal mucin repeat domain, three epidermal growth factor-like sequences, a SEA module, a transmembrane domain, and a cytoplasmic tail (GenBank accession no. AF286113). MUC13 mRNA is expressed most highly in the large intestine and trachea, and at moderate levels in the kidney, small intestine, appendix, and stomach. In situ hybridization in murine tissues revealed expression in intestinal epithelial and lymphoid cells. Immunohistochemistry demonstrated the human MUC13 protein on the apical membrane of both columnar and goblet cells in the gastrointestinal tract, as well as within goblet cell thecae, indicative of secretion in addition to presence on the cell surface. MUC13 is cleaved, and the ␤-subunit containing the cytoplasmic tail undergoes homodimerization. Including MUC13, there are at least five cell surface mucins expressed in the gastrointestinal tract.

X-linked West syndrome, also called "X-linked infantile spasms" (ISSX), is characterized by early-onset generalized seizures, hypsarrhythmia, and mental retardation. Recently, we have shown that the majority of the X-linked families with infantile spasms carry mutations in the aristaless-related homeobox gene (ARX), which maps to the Xp21.3-p22.1 interval, and that the clinical picture in these patients can vary from mild mental retardation to severe ISSX with additional neurological abnormalities. Here, we report a study of two severely affected female patients with apparently de novo balanced X;autosome translocations, both disrupting the serine-threonine kinase 9 (STK9) gene, which maps distal to ARX in the Xp22.3 region. We show that STK9 is subject to X-inactivation in normal female somatic cells and is functionally absent in the two patients, because of preferential inactivation of the normal X. Disruption of the same gene in two unrelated patients who have identical phenotypes (consisting of early-onset severe infantile spasms, profound global developmental arrest, hypsarrhythmia, and severe mental retardation) strongly suggests that lack of functional STK9 protein causes severe ISSX and that STK9 is a second X-chromosomal locus for this disorder.

Sex in mammals is genetically determined and is defined at the cellular level by sex chromosome complement (XY males and XX females). The Y chromosome-linked gene sex-determining region Y (SRY) is believed to be the master initiator of male sex determination in almost all eutherian and metatherian mammals, functioning to upregulate expression of its direct target gene Sry-related HMG box-containing gene 9 (SOX9). Data suggest that SRY evolved from SOX3, although there is no direct functional evidence to support this hypothesis. Indeed, loss-of-function mutations in SOX3 do not affect sex determination in mice or humans. To further investigate Sox3 function in vivo, we generated transgenic mice overexpressing Sox3. Here, we report that in one of these transgenic lines, Sox3 was ectopically expressed in the bipotential gonad and that this led to frequent complete XX male sex reversal. Further analysis indicated that Sox3 induced testis differentiation in this particular line of mice by upregulating expression of Sox9 via a similar mechanism to Sry. Importantly, we also identified genomic rearrangements within the SOX3 regulatory region in three patients with XX male sex reversal. Together, these data suggest that SOX3 and SRY are functionally interchangeable in sex determination and support the notion that SRY evolved from SOX3 via a regulatory mutation that led to its de novo expression in the early gonad.

The ETS family of genes are implicated in cancers such as Ewings sarcoma, acute myeloid leukemia and chronic myelomoncytic leukemia. Further, they have important functions in embryonic development. Hence, identi®ca-tion and characterization of members of this family are important. We identify a novel ETS family member, ELF3, and report its human and murine cDNA sequences. The mouse cDNA has an alternatively spliced transcript with an extra 60 bp inserted. Hence we present the organization of the murine Elf3 gene together with its exon/intron structure. This gene consists of 9 exons and 8 introns spanning 4.8 kb. ELF3 binds and transactivates ETS sequences and interestingly also shows the ability to bind a GGAT-like purine core, a preferential ETS1/ETS2 type binding site. The expression of ELF3, unlike most other ETS family members, is absent in hematopoietic cells and hematopoietic organs in humans and mice. Intriguingly, the gene is speci®cally expressed in cell lines of epithelial origin and in organs such as lung, stomach, intestine, kidney that have specialized epithelial cells. We localize the human gene to 1q32.2, a region that is ampli®ed in epithelial tumors of the breast, lung and prostate. Finally, we show that ELF3 expression is increased in a lung carcinoma and adenocarcinoma, as compared to normal tissue. ELF3 is also expressed in cell lines derived from lung cancers. These results suggest that this novel ETS gene may be involved in lung tumorigenesis.

The Omega class glutathione transferases (GSTs) have been identified in many organisms, including human, mouse, rat, pig, Caenorhabditis eglands and Drosophila melanogaster. These GSTs have poor activity with common GST substrates, but exhibit novel glutathione-dependent thioltransferase, dehydroascorbate reductase and monomethylarsonate reductase activities, and modulate Ca release by ryanodine receptors. An investigation of the genomic organization of human GSTO1 identified a second actively transcribed member of the Omega class (GSTO1). Both GSTO1 and GSTO2 are composed of six exons and are separated by 7.5 kb on chromosome 10q24.3. A third sequence that appears to be a reverse-transcribed pseudogene (GSTO3p) has been identified on chromosome 3. GSTO2 has 64% amino acid identity with GSTO1 and conserves the cysteine residue at position 32, which is thought to be important in the active site of GSTO1. Expression of GSTO2 mRNA was seen in a range of tissues, including the liver, kidney, skeletal muscle and prostate. The strongest GSTO2 expression was in the testis, which also expresses a larger transcript than other tissues. Characterization of recombinant GSTO2 has been limited by its poor solubility. Two functional polymorphisms of GSTO1 have been identified. One alters a splice junction and causes the deletion of E155 and another results in an A140D substitution. Characterization of these variants revealed that the A140D substitution affects neither heat stability, nor activity towards 1-chloro-2,4-dinitrobenzene or hydroxyethyl disulphide. In contrast, deletion of residue E155 appears to contribute towards both a loss of heat stability and increased enzymatic activity.

The 16p13.3 breakpoints of two de novo translocations of chromosome 16, t(1;16) and t(14;16), were shown by initial mapping studies to have physically adjacent breakpoints. The translocations were ascertained in patients with abnormal phenotypes characterized by predominant epilepsy in one patient and mental retardation in the other. Distamycin/DAPI banding showed that the chromosome 1 breakpoint of the t(1;16) was in the pericentric heterochromatin therefore restricting potential gene disruption to the 16p13.3 breakpoint. The breakpoints of the two translocations were localized to a region of 3.5 and 115 kb respectively and were approximately 900 kb apart. The mapping was confirmed by fluorescence in situ hybridization (FISH) of clones that spanned the breakpoints to metaphase spreads derived from the patients. The mapping data showed both translocations disrupted the ataxin-2-binding protein 1 (A2BP1) gene that encompasses a large genomic region of 1.7 Mb. A2BP1 encodes a protein that is known to interact with the spinocerebellar ataxia type 2 (SCA2) protein. It is proposed that disruption of the A2BP1 gene is a cause of the abnormal phenotype of the two patients. Ninety-six patients with sporadic epilepsy and 96 female patients with mental retardation were screened by SSCP for potential mutations of A2BP1. No mutations were found, suggesting that disruption of the A2BP1 gene is not a common cause of sporadic epilepsy or mental retardation.Keywords A2BP1 AE Chromosome 16 AE Spinocerebellar ataxia binding protein AE De novo translocation De novo chromosome rearrangements are associated with an increased risk of congenital malformations (Warburton 1991). Disruption of a critical gene at the translocation breakpoint is thought to be the basis for this increased risk. We report the finding of two patients with de novo translocations that involve a breakpoint at 16p13.3, show that there is disruption of the ataxin-2-binding protein 1 (A2BP1) gene by these 16p13.3 breakpoints, and propose that the disruption of A2BP1 is the basis for the patients' clinical phenotypes.The first of the de novo translocations was ascertained in a boy with severe intellectual and developmental retardation (developmental skills at 2-2.5 years when examined at 4 years 11 months) but with no dysmorphic features other than strabismus and down-turned angles of the mouth. There was a single recorded episode of fitting at 5 days old. Chromosome analysis showed at(1;16)(q12;p13.3). Parental karyotypes were normal. Both parents were considered to have mild intellectual disability. Distamycin A/DAPI, which stains the pericentromeric heterochromatin of chromosomes 1 and 16, was used to stain the chromosomes (Fig. 1a). The der(1)t(1;16) showed a single band; the der(16) had two bands, one representing the 16 heterochromatin and the other at the 16p13.3 breakpoint derived from chromosome 1 heterochromatin (Fig. 1a). This observation is consistent with the location of the chromosome 1 breakpoint within the 1q12 heterochromatin. If the boy'...