HRPT2, encoding parafibromin, is mutated in hyperparathyroidism-jaw tumor syndrome.

We report here the identification of a gene associated with the hyperparathyroidism-jaw tumor (HPT-JT) syndrome. A single locus associated with HPT-JT (HRPT2) was previously mapped to chromosomal region 1q25-q32. We refined this region to a critical interval of 12 cM by genotyping in 26 affected kindreds. Using a positional candidate approach, we identified thirteen different heterozygous, germline, inactivating mutations in a single gene in fourteen families with HPT-JT. The proposed role of HRPT2 as a tumor suppressor was supported by mutation screening in 48 parathyroid adenomas with cystic features, which identified three somatic inactivating mutations, all located in exon 1. None of these mutations were detected in normal controls, and all were predicted to cause deficient or impaired protein function. HRPT2 is a ubiquitously expressed, evolutionarily conserved gene encoding a predicted protein of 531 amino acids, for which we propose the name parafibromin. Our findings suggest that HRPT2 is a tumor-suppressor gene, the inactivation of which is directly involved in predisposition to HPT-JT and in development of some sporadic parathyroid tumors.

An expression-site-associated gene family of trypanosomes is expressed in vivo and shows homology to a variant surface glycoprotein gene.

Utilizing first-strand cDNA from different stages, a gene family was identified that is expressed in bloodstream form trypanosomes but not in cultured procyclic forms. This family of 50-100 genes, termed bloodstream-specific 1 (BS1), shares a chromosomal distribution pattern similar to the variant surface glycoprotein (VSG) genes and the expression-site-associated genes (ESAGs). The BS1 genes are expressed in several variants of Trypanosoma brucei brucei and in Trypanosoma brucei gambiense. Sequence analysis of five members of this gene family reveals the recently described ESAG 6 and ESAG 7 genes as well as the ESAG X gene to be members of this family. We have been unable to localize the BS1 gene product in the cell but show that chronically infected rabbit serum recognizes recombinant BS1 protein arguing for expression in vivo. Finally we note that the derived protein sequence for the BS1 genes suggests an evolutionary relationship with at least one variant surface glycoprotein gene, and hence these studies may provide clues to understanding the molecular origins of antigenic variation in trypanosomes.

Monoclonal antibodies to the extracellular domain of HIV-1IIIB gp160 that neutralize infectivity, block binding to CD4, and react with diverse isolates.

Ten monoclonal antibodies prepared against a soluble, recombinant form of gp160, derived from the IIIB isolate of HIV-1, were characterized. Four of the antibodies neutralized HIV-1IIIB infectivity in vitro, three blocked the binding of recombinant gp120 to CD4, three were reactive with gp41, and one preferentially reacted with an epitope on gp120 within the gp160 precursor. All three CD4 blocking antibodies bound to distinct epitopes, with one mapping to the C1 domain, one mapping to the C4 domain, and one reactive with a conformation-dependent, discontinuous epitope. Of these, the antibody reactive with the discontinuous epitope exhibited neutralizing activity against homologous and heterologous strains of HIV-1. The binding of these monoclonal antibodies to a panel of seven recombinant gp120s prepared from diverse isolates of HIV-1 was measured, and monoclonal antibodies with broad cross reactivity were identified. The epitopes recognized by 7 of the 10 monoclonal antibodies studied were localized by their reactivity with synthetic peptides and with fragments of gp120 expressed as fusion proteins in a lambda gt-11 gp160 epitope library.

Uterine tumours are a phenotypic manifestation of the hyperparathyroidism-jaw tumour syndrome.

The hyperparathyroidism-jaw tumour (HPT-JT) syndrome is an autosomal dominant disorder characterized by parathyroid tumours, which are frequently carcinomas, and ossifying jaw fibromas. In addition, some patients may develop renal tumours and cysts. The gene causing HPT-JT, which is referred to as HRPT2 and is located on chromosome 1q31.2, encodes a 531 amino acid protein called PARAFIBROMIN. To date 42 mutations, of which 22 are germline, have been reported and 97% of these are inactivating and consistent with a tumour suppressor role for HRPT2. We have investigated another four HPT-JT families for germline mutations, searched for additional clinical phenotypes, and examined for a genotype-phenotype correlation. Mutations were found in two families. One family had a novel deletional-insertion at codon 669, and the other had a 2 bp insertion at codon 679, which has been reported in four other unrelated patients. These five unrelated patients and their families with the same mutation were not found to develop the same tumours, thereby indicating an absence of a genotype-phenotype correlation. An analysis of 33 HPT-JT kindreds revealed that affected women in 13 HPT-JT families suffered from menorrhagia in their second to fourth decades. This often required hysterectomy, which revealed the presence of uterine tumours. This resulted in a significantly reduced maternal transmission of the disease. Thus, the results of our analysis expand the spectrum of HPT-JT-associated tumours to include uterine tumours, and these may account for the decreased reproductive fitness in females from HPT-JT families.

A physical map encompassing GP2B, EPB3, D17S183, D17S78, D17S1183, and D17S1184.

The q21 region of chromosome 17 contains the gene BRCA1, which is involved in familial early-onset breast and ovarian cancers. A physical map of a region that extends from a distal boundary of the BRCA1 region, D17S78, to GP2B has been constructed. The map consists of 30 STSs, including 2 new short tandem repeat polymorphic markers. The contig is composed of a mixture of 7 YACs, 5 P1 plasmids, and 14 cosmids and was ordered by STS-content mapping.

A P1-based physical map of the region from D17S776 to D17S78 containing the breast cancer susceptibility gene BRCA1.

BRCA1, a breast and ovarian cancer susceptibility locus, has been isolated and maps to 17q21. A physical map of the BRCA1 region which extended from the proximal boundary at D17S776 to the distal boundary at D17S78 was constructed and consists of 51 sequence tagged sites (STSs) from P1 and YAC ends, nine new short-tandem repeat (STR) polymorphic markers, and eight identified genes. The contig, which spans the estimated 2.3 Mb region, contains 29 P1s, 11 YACs, two BACs, and one cosmid. Based on key recombinants in two linked families, BRCA1 was further localized to a region bounded by D17S1321 on the proximal side and D17S1325 on the distal side. Within this estimated 600 kb region, the contig was composed completely of P1s and BACs ordered by STS-content mapping and confirmed by DNA restriction fragment fingerprinting.

Hyperparathyroidism-jaw tumor syndrome: the HRPT2 locus is within a 0.7-cM region on chromosome 1q.

Hyperparathyroidism-jaw tumor syndrome (HPT-JT) is an autosomal dominant disease characterized by the development of multiple parathyroid adenomas and multiple fibro-osseous tumors of the maxilla and mandible. Some families have had affected members with involvement of the kidneys, variously reported as Wilms tumors, nephroblastomas, and hamartomas. The HPT-JT gene (HRPT2) maps to chromosome 1q25-q31. We describe further investigation of two HPT-JT families (K3304 and K3349) identified through the literature. These two expanded families and two previously reported families were investigated jointly for linkage with 21 new, closely linked markers. Multipoint linkage analysis resulted in a maximum LOD score of 7.83 (at recombination fraction 0) for markers D1S2848-D1S191. Recombination events in these families reduced the HRPT2 region to approximately 14.7 cM. In addition, two of these four study families (i.e., K3304 and K11687) share a 2.2-cM length of their (expanded) affected haplotype, indicating a possible common origin. Combining the linkage data and shared-haplotype data, we propose a 0.7-cM candidate region for HRPT2.

Strain specificity and binding affinity requirements of neutralizing monoclonal antibodies to the C4 domain of gp120 from human immunodeficiency virus type 1.

The binding properties of seven CD4-blocking monoclonal antibodies raised against recombinant gp120 of human immunodeficiency virus type 1 strain MN (HIV-1MN) and two CD4-blocking monoclonal antibodies to recombinant envelope glycoproteins gp120 and gp160 of substrain IIIB of HIVLAI were analyzed. With a panel of recombinant gp120s from seven diverse HIV-1 isolates, eight of the nine antibodies were found to be strain specific and one was broadly cross-reactive. Epitope mapping revealed that all nine antibodies bound to epitopes located in the fourth conserved domain (C4) of gp120. Within this region, three distinct epitopes could be identified: two were polymorphic between HIV-1 strains, and one was highly conserved. Studies with synthetic peptides demonstrated that the conserved epitope, recognized by antibody 13H8, was located between residues 431 and 439. Site-directed mutagenesis of gp120 demonstrated that residue 429 and/or 432 was critical for the binding of the seven antibodies to gp120 from HIV-1MN. Similarly, residues 423 and 429 were essential for the binding of monoclonal antibody 5C2 raised against gp120 from HIV-1IIIB. The amino acids located at positions 423 and 429 were found to vary between strains of HIV-1 as well as between molecular clones derived from the MN and LAI isolates of HIV-1. Polymorphism at these positions prevented the binding of virus-neutralizing monoclonal antibodies and raised the possibility that HIV-1 neutralization serotypes may be defined on the basis of C4 domain sequences. Analysis of the binding characteristics of the CD4-blocking antibodies demonstrated that their virus-neutralizing activity was directly proportional to their gp120-binding affinity. These studies account for the strain specificity of antibodies to the C4 domain of gp120 and demonstrate for the first time that antibodies to this region can be as effective as those directed to the principal neutralizing determinant (V3 domain) in neutralizing HIV-1 infectivity.

Neutralization of multiple laboratory and clinical isolates of human immunodeficiency virus type 1 (HIV-1) by antisera raised against gp120 from the MN isolate of HIV-1.

Vaccines prepared from the envelope glycoprotein, gp120, of the common laboratory isolate of human immunodeficiency virus type 1 (HIV-1) (IIIB/LAV-1) elicit antibodies that neutralize the homologous virus but show little if any cross-neutralizing activity. This may be because the principal neutralizing determinant (PND) of gp120 is highly unusual in the IIIB/LAV-1 strain and is not representative of those found in the majority of field isolates. We have now examined the immunogenicity of recombinant gp120 prepared from the MN strain of HIV-1 (MN-rgp120), whose PND is thought to be representative of approximately 60% of the isolates in North America. Our results show that MN-rgp120 is a potent immunogen and elicits anti-gp120 titers comparable to those found in HIV-1-infected individuals. While both MN-rgp120 and IIIB-rgp120 induced antibodies able to block gp120 binding to CD4, strain-specific and type-common blocking antibodies were detected. Finally, antibodies to MN-rgp120 but not to IIIB-rgp120 were effective in neutralizing a broad range of laboratory and clinical isolates of HIV-1. These studies demonstrate that susceptibility or resistance to neutralization by antibodies to gp120 correlates with the PND sequence and suggest that the problem of antigenic variation may not be insurmountable in the development of an effective AIDS vaccine.

Nitric oxide synthase type 2 promoter polymorphisms, nitric oxide production, and disease severity in Tanzanian children with malaria.

Nitric oxide (NO) plays an important role in host resistance to infection with a variety of organisms. Two recent reports from Gabon and Gambia identified associations of malaria disease severity with the inducible NO synthase (NOS2) promoter G-954C and short allele (<11 repeats) pentanucleotide microsatellite polymorphisms, respectively. It was postulated that there would be a correlation of these polymorphisms with malaria disease severity and with measures of NO production in our cohort of Tanzanian children with malaria. In Tanzanian children, 15% were heterozygous or homozygous for the G-954C polymorphism, and 13% had the short-allele microsatellite polymorphism. There was no significant correlation of either polymorphism with disease severity or with measures of NO production and NOS2 expression. Black and white Americans differed significantly in the frequencies of these polymorphisms. The various association of these gene polymorphisms with malaria severity in different populations underscores the complexity of host resistance to malaria.

A promoter polymorphism in the gene encoding interleukin-12 p40 (IL12B) is associated with mortality from cerebral malaria and with reduced nitric oxide production.

Interleukin-12 (IL-12) is an important regulatory cytokine in infection and immunity. Administration of IL-12 may reduce complications of severe malaria in rodents. Polymorphisms in IL12B, the gene encoding the IL-12 p40 subunit, influence the secretion of IL-12 and susceptibility to Type 1 diabetes. We therefore investigated whether IL12B polymorphisms may affect the outcome of severe malaria. Homozygosity for a polymorphism in the IL12B promoter was associated with increased mortality in Tanzanian children having cerebral malaria but not in Kenyan children with severe malaria. Furthermore, homozygotes for the IL12B promotor polymorphism had decreased production of nitric oxide, which is in part regulated by IL-12 activity. These studies suggest that IL12B polymorphisms, via regulation of IL-12 production, may influence the outcome of malaria infection in at least one African population.