Hartnup disorder, an autosomal recessive defect named after an English family described in 1956 (ref. 1), results from impaired transport of neutral amino acids across epithelial cells in renal proximal tubules and intestinal mucosa. Symptoms include transient manifestations of pellagra (rashes), cerebellar ataxia and psychosis 1,2 . Using homozygosity mapping in the original family in whom Hartnup disorder was discovered, we confirmed that the critical region for one causative gene was located on chromosome 5p15 (ref. 3). This region is homologous to the area of mouse chromosome 13 that encodes the sodium-dependent amino acid transporter B 0 AT1 (ref. 4). We isolated the human homolog of B 0 AT1, called SLC6A19, and determined its size and molecular organization. We then identified mutations in SLC6A19 in members of the original family in whom Hartnup disorder was discovered and of three Japanese families. The protein product of SLC6A19, the Hartnup transporter, is expressed primarily in intestine and renal proximal tubule and functions as a neutral amino acid transporter.Despite molecular characterization of other proximal tubule transporters, the neutral amino acid carrier defective in Hartnup disorder (OMIM 2345000) has resisted genetic identification 2 . We carried out homozygosity mapping and fine mapping in ten members of two consanguineous families (the siblings in whom Hartnup disorder was originally discovered 1 ; family A; Fig. 1a) and in siblings from the US 5 (family B; Fig. 1a). We found linkage of Hartnup disorder to 5p15 only in family A, with a maximum combined multipoint lod score of 2.31 at 11.24 cM (P ¼ 0.01). This confirmed our previous results showing linkage to chromosome 5p15 (ref.3). In family B, we obtained a maximum multipoint lod score of À2.40 at 15.81 cM.We simultaneously pursued two mouse monoamine transporterrelated orphan genes, Slc6a18 (also called Xtrp2; ref. 6) and Slc6a19 (encoding B 0 AT1; ref. 4). These members of the SLC6 family of transporters map to the mouse chromosomal region that is homologous to human chromosome 5p15. Both Slc6a18 and Slc6a19 showed abundant expression in mouse kidney, as assessed by real time RT-PCR (Fig. 2a). Immunohistochemistry confirmed expression of mouse B 0 AT1 at the brush border of small intestine (data not shown) and kidney proximal tubule cells (Fig. 2b).The human homolog, B 0 AT1, is encoded by the predicted locus SLC6A19, with a 2,022-bp open reading frame. PCR amplification using human kidney cDNA produced a 1,905-bp product with 100% identity to SLC6A19 sequence. We next determined the genomic organization of SLC6A19, which has a stop codon 28 bases before the ATG in the 5¢ untranslated region. SLC6A19 has 12 coding exons. The B 0 AT1 protein contains 634 amino acids and 12 predicted transmembrane regions (Fig. 1b). In a panel of human cDNAs, we detected robust expression of SLC6A19 in kidney and small intestine, with minimal expression in pancreas (Fig. 2c). SLC6A19 was also expressed in stomach, liver, duodenum and ileocecum (data n...

Hereditary hemorrhagic telangiectasia (HHT or Rendu-Osler-Weber syndrome) is an autosomal dominant disorder characterized by aberrant vascular development. We report here a genetic epidemiologic study in a county, A, in the Akita prefecture (population 1.2 million) located in northern Japan. Nine HHT patients who had been referred to tertiary-care hospitals were located in and near the study county. A total of 137 pedigree members were traced of which 81 were alive and 32 were affected by HHT. Complications associated with cerebral or pulmonary arteriovenous malformations were proven in six out of seven families. Linkage analysis in two large families revealed a weak yet suggestive linkage to the HHT1 locus (encoding endoglin; ENG). Three novel mutations were found in four families, all of which led to a frameshift: a G to C transversion at the splicing donor site of intron 3 (Inv3+1 G>C) in one family, one base pair insertion (A) at nucleotide 828 (exon 7) of the endoglin cDNA in two large families (c.828-829 ins A), and a four base pair deletion (AAAG) beginning with nucleotide 1120 (exon 8) of the endoglin cDNA (c.1120-1123 delAAAG) in one family. The insertion of A in exon 11 (c.1470-1471 insA) mutation found in one family has also been reported in a European family. No endoglin gene mutations were found in two families. The population prevalence of HHT in the county was estimated to be 1:8,000 approximately 1:5,000, roughly comparable with those reported in European and U.S. populations, which is contradictory to the traditional view that HHT is rare among Asians. We recommend that families with HHT be screened for gene mutations in order that high-risk individuals receive early diagnosis and treatment initiation that will substantially alter their clinical course and prognosis.

No abstract

No abstract

DNA damage induced by Ni(II) plus H2O2 was investigated by a DNA sequencing technique using 32P-5'-end-labeled DNA fragments obtained from human c-Ha-ras-1 protooncogene. Ni(II) induced strong DNA cleavage in the presence of H2O2 even without piperidine treatment. Piperidine-labile sites were induced frequently at cytosine, thymine and guanine residues, and rarely at adenine residue. Diethylene-triamine N,N,N',N",N"-pentaacetic acid inhibited the DNA damage. In experiments with singlet oxygen scavengers, sodium azide and dGMP inhibited the DNA damage completely, whereas neither 1,4-diazabicyclo[2.2.2]octane nor dimethylfuran inhibited it. Among hydroxyl radical scavengers, dimethylsulfoxide and sodium formate inhibited the DNA damage considerably, whereas ethanol and mannitol did not. Methionine and methional inhibited the DNA damage completely. The results suggest that Ni(II) ion binds to DNA and subsequently reacts with H2O2 to form active species, which cause DNA damage. The possibility of Ni(II) plus H2O2-mediated DNA damage in vivo is discussed relative to the molecular mechanism of nickel carcinogenesis.