Identification of mutations (D128G, H141L) in the liver arginase gene of patients with hyperargininemia.
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Biomedical subjects
Publications and source records attributed to B K Goodman.
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Functional and DNA binding analyses were used to investigate transcriptional regulation of liver arginase, a mammalian urea cycle enzyme with marked tissue specificity. Reporter constructs containing the proximal 111 bp of the gene from man and Macaca fascicularis showed over sixfold background activity in HepG2 hepatoma cells, which express significant levels of liver arginase, and 12-fold background activity in minimally expressing HEK cells. Longer constructs, active in both cell lines, showed greater activity in the liver cell line. The constructs showed no activity in arginase-negative NIH 3T3 fibroblasts. A 54-bp dyad insert present in the human sequence and absent in M. fascicularis did not affect function. DNA binding analyses localized multiple liver-specific complexes as well as complexes shared among cell types. Little binding was evident in fibroblast extracts. Despite liver-specific binding, there was no evidence of a strong liver-specific enhancer. HEK and NIH 3T3 nuclear extracts showed strikingly different patterns of DNA binding. These studies demonstrate that molecular regulation of liver arginase transcription is complex and that control mechanisms differ among tissue types.
We have explored the molecular pathology in 28 individuals homozygous or heterozygous for liver arginase deficiency (hyperargininemia) by a combination of Southern analysis, western blotting, DNA sequencing, and PCR. This cohort represents the majority of arginase-deficient individuals worldwide. Only 2 of 15 homozygous patients on whom red blood cells were available had antigenically cross-reacting material as ascertained by western blot analysis using anti-liver arginase antibody. Southern blots of patient genomic DNAs, cut with a variety of restriction enzymes and probed with a near-full-length (1,450-bp) human liver arginase cDNA clone, detected no gross gene deletions. Loss of a TaqI cleavage site was identified in three individuals: in a homozygous state in a Saudi Arabian patient at one site, at a different site in homozygosity in a German patient, and in heterozygosity in a patient from Australia. The changes in the latter two were localized to exon 8, through amplification of this region by PCR and electrophoretic analysis of the amplified fragment after treatment with TaqI; the precise base changes (Arg291X and Thr290Ser) were confirmed by sequencing. It is interesting that the latter nucleotide variant (Thr290Ser) was found to lie adjacent to the TaqI site rather than within it, though whether such a conservative amino acid substitution represents a true pathologic mutation remains to be determined. We conclude that arginase deficiency, though rare, is a heterogeneous disorder at the genotypic level, generally encompassing a variety of point mutations rather than substantial structural gene deletions.
We report the case of a 26-year-old man with von Hippel-Lindau syndrome (VHL) and two renal cell carcinomas (RCC), one of which was studied cytogenetically. Chromosomal analysis of the RCC showed a translocation that involved chromosomes 3 and 8 with subsequent loss of the derivative chromosome 8. The patient's peripheral lymphocytes showed a normal karyotype that indicated that there was not a constitutional chromosomal translocation. This is the third reported case of RCC in a patient with VHL in which loss of a portion of the short arm of chromosome 3 (3p) has occurred. Similar chromosomal changes that involve 3p have been reported in both familial and sporadic cases of RCC and have led to speculation that a tumor suppressor gene may be located in this region. Cytogenetic characterization of renal tumors could assume increasing significance in the diagnosis and classification of RCC and potentially may guide therapy. These studies may also lead to a better understanding of the biologic behavior of RCC and result in more informed patient evaluation and counseling.
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PURPOSE: To illustrate the use of bacterial artificial chromosome (BAC) clone panels for molecular cytogenetic analysis of complex chromosome rearrangements (CCRs). METHODS: High resolution cytogenetics followed by fluorescence in situ hybridization (FISH) analysis using chromosome band-specific BAC probes, in addition to commercially available probes. RESULTS: High resolution cytogenetics in conjunction with FISH using commercially available probes proved inadequate to resolve problems in characterizing a balanced CCR in the mother of a patient who had inherited an unbalanced form of the CCR. Accurate interpretation of the CCR and the unbalanced rearrangement in the patient as trisomy 7p12.2-->p21.3 was accomplished only through use of the BAC clone panel. CONCLUSION: Use of BAC clone panels can enhance the power of FISH analysis in defining chromosome rearrangements that cannot be resolved by high resolution chromosome analysis.
Soft tissue perineuriomas are rare mesenchymal tumors that are derived from perineurial cells of the peripheral nerve sheath. Although the histological and immunohistochemical features of soft tissue perineuriomas are well described, little is known regarding the cytogenetic abnormalities in these tumors. Herein, we describe a case of a large (12.2 cm) soft tissue perineurioma that arose in the thigh of a 26-year-old Caucasian female. Histologically, the tumor was composed of a diffuse to fascicular arrangement of spindle cells with bland, elongated nuclei with long, thin, tapering cytoplasmic processes. The immunohistochemical profile was consistent with a perineurial cell origin with expression of epithelial membrane antigen, vimentin, and collagen type IV. Cytogenetic evaluation revealed loss of chromosome 13 as the sole abnormality in the majority of examined cells. In contrast to previous reports, we were unable to demonstrate deletion or structural abnormalities of chromosome 22 by either fluorescence in situ hybridization (FISH) or metaphase cytogenetics. This is the first report of loss of chromosome 13 in soft tissue perineurioma. Although never described in this group of neoplasms, loss of chromosome 13 has been identified in a large number of other soft tissue tumors, particularly sarcomas and malignant peripheral nerve sheath tumors. Herein, we discuss this case and provide a review of the literature.