Kimitaka Sakamoto

Common characteristics of mutant adenine phosphoribosyltransferases from four separate Japanese families with 2,8-dihydroxyadenine urolithiasis associated with partial enzyme deficiencies

Summary2,8-Dihydroxyadenine urolithiasis associated with partial deficiencies of adenine phosphoribosyltransferase (APRT) has been found only among Japanese families. All Caucasian patients with the same lithiasis are completely deficient in this enzyme. Partially purified APRT from one of the Japanese families with the lithiasis associated with a partial deficiency of APRT had a reduced affinity for 5-phosphoribosyl-1-pyrophosphate (PRPP). In the present investigations, we have shown that this characteristic is common in mutant enzymes from all the four separate Japanese urolithiasis families associated with partial APRT deficiencies so far tested. The mutant enzymes also had several other characteristics in common including increased resistance to heat in the absence of PRPP and reduced sensitivity to the stabilizing effect of PRPP. These data suggest that these families have a common mutant allele (APRT*J) at the APRT gene locus.

Renal Primitive Neuroectodermal Tumor: A Morphologic, Cytogenetic, and Molecular Analysis with the Establishment of Two Cultured Cell Lines

We report two patients with renal primitive neuroectodermal tumor (PNET) in whom the diagnosis was established by both a cytogenetic and a molecular analysis. Histologically, both renal tumors were composed of uniform immature round cells with a positive immunoreactivity for 013 (p30/32 MIC2). The cytogenetic analysis with in situ hybridization (chromosome painting) demonstrated reciprocal translocation t(11;22)(q24;q12) specific to PNET in the cultured cells derived from each tumor. The reverse transcriptase-polymerase chain reaction (RT-PCR) in both tumors demonstrated EWS/ FLI-1 fusion transcripts, representing the molecular equivalent of t(11; 22). A Southern blot analysis also confirmed EWS gene rearrangement in both renal tumors. In addition, the authors also established two new cell lines (designated as FU-RPNT-1 and FU-RPNT-2) from renal PNETs. When transplanted into athymic mice, FU-RPNT-1 and FU-RPNT-2 reproduced and maintained the morphologic and molecular characteristics of the original tumors. In conclusion, the detection of t(11; 22) and EWS/FLI-1 fusion transcripts is considered to provide a novel adjunctive method for diagnosing renal PNET. These newly established cell lines thus may be used to investigate the biologic behavior related to renal PNETs.

Dihydroxyadenine urolithiasis in children with partial deficiency of adenine phosphoribosyltransferase.

Urolithiasis composed of 2,8-dihydroxyadenine is not only formed in a complete defect of adenine phosphoribosyltransferase, but also in a partial deficiency of this enzyme. To our knowledge these cases reported in this paper are the third and fourth cases of dihydroxyadenine urinary calculi in patients with partial deficiency of adenine phosphoribosyltransferase.

Catheterless Cutaneous Ureterostomy

New procedures for tubeless cutaneous ureterostomy are described. The fundamental principles of the methods are 1) an everted ureteral nipple formation combined with a triangular skin flap as a permanent stoma and 2) a 2-stage operation to obtain a viable ureteral nipple against slough and retraction.

XX/XY Chromosomal Mosaicism Presenting a Chordee Without Hypospadias Associated With Scrotal Transposition

Abstract XX/XY chromosomal mosaicism, except for hermaphroditism, is seen rarely with hypospadias. To our knowledge this is the first case of XX/XY mosaicism presenting a chordee without hypospadias associated with scrotal transposition.

Chronic Incomplete Obstruction of the Ureter: A New Experimental Model

To produce a chronic moderate hydronephrosis in dog, a method of partial ureteral occlusion using a specially designed polypropylene obturator was developed. In 11 of 14 dogs undergoing this procedure, excretory urography constantly revealed a moderate degree of hydronephrosis persisting for 7 weeks. Combination of this method in one ureter with the vaginal-cuff cutaneous ureterostomy, previously reported, in the contralateral ureter is a useful model for split renal function study of unilateral chronic hydronephrosis or obstructive nephropathy analogous to that of clinical case.

Intervention of somatic mutational events in vivo by a germline defect at the adenine phosphoribosyltransferase locus

Abstract Both germline and somatic mutations are known to affect phenotypes of human cells in vivo. In previous studies, we cloned mutant peripheral blood T cells from germline heterozygous humans for adenine phosphoribosyltransferase (APRT) (EC 2.4.2.7) deficiency and found that approximately 1.3 × 10–4 peripheral T cells had undergone in vivo somatic mutations. Loss of heterozygosity (LOH) was the major cause of the mutations at the APRT locus since approximately 80% of the mutant T cell clones exhibited loss of normal alleles. In the present study, we identified three heterozygous individuals for APRT deficiency (representing two separate families), in whom none of the somatic mutant cells exhibited LOH at the APRT locus. The germline mutant APRT alleles of these heterozygotes from two unrelated families had the same gross DNA abnormalities detectable by Southern blotting. None of the germline mutant APRT alleles so far reported had such gross DNA abnormalities. The data suggest that the germline mutation unique to these heterozygous individuals is associated with the abrogation of LOH in somatic cells. The absence of LOH at a different locus has already been reported in vitro in an established cell line but the present study describes the first such event in vivo in human individuals.