Nail-patella syndrome (NPS) is an autosomal dominant disease characterized by dysplastic nails, absent or hypoplastic patellae, elbow dysplasia, and nephropathy. Recently, it was shown that NPS is the result of heterozygous mutations in the LIM-homeodomain gene, LMX1B. Subsequently, many mutations of the LMX1B gene have been reported in NPS patients. However, functional analyses of the mutant proteins have been performed in only a few mutations. Furthermore, the mechanisms of dominant inheritance in humans have not been established. In the present study, we analyzed the LMX1B gene in three Japanese patients with NPS and identified two novel mutations, 6 nucleotide deletion (⌬246⌵ 247Q) and V242L. These two mutations are located in the homeodomain of LMX1B.Functional analyses of the LMX1B mutants revealed that these mutants had diminished transcriptional activity and had lost DNA binding ability. Furthermore, we demonstrated that each mutant did not manifest a dominant-negative effect on the transcriptional activity of wild-type LMX1B. These results suggested that NPS is caused by loss-of-function mutations of LMX1B, and haploinsufficiency of LMX1B should be the predominant pathogenesis of NPS in humans. Nail-patella syndrome (NPS; MIM#161200) is an autosomal dominant disease characterized by dysplastic nails, absent or hypoplastic patellae, elbow dysplasia, iliac horns, and, in some cases, open-angle glaucoma and nephropathy (1-3). Nail dysplasia is the most constant feature of NPS observed at birth. The most serious aspect of NPS is nephropathy, which might develop end-stage renal failure. Although development to endstage renal failure is usually slow, a minority of cases have been reported to show rapid progression during early childhood (3,4).It has been demonstrated that mutations of the LMX1B gene, which is located on chromosome 9q34, result in NPS (5-8). LMX1B is a member of the LIM-homeodomain family of transcription factors that are involved in body-pattern formation during development (9,10). These proteins contain two cysteine-rich zinc-binding motifs (LIM-A and LIM-B domain) at their amino termini that are important in mediating proteinprotein interactions and a homeodomain involved in DNA binding (9,10). The LMX1B-mediated transactivation presumably requires interaction with a transcriptional complex including a helix-loop-helix protein, E47/shPan1 (11,12). During embryogenesis, Lmx1b is strongly expressed in dorsal mesenchymal tissues in mice (12). Lmx1bϪ/Ϫ mice showed the absence of dorsal limb structures and duplication of ventral structures (7). These findings suggest that Lmx1b is essential for dorsoventral patterning during development and that the skeletal phenotype of NPS is the result of a deficiency in dorsoventral patterning. LMX1B is also expressed in human fetal and adult kidneys (5).From the analysis of Lmx1bϪ/Ϫ mice, it was suggested that LMX1B regulates the expression of type IV collagen ␣3 and ␣4 and podocin and that Lmx1b mutations cause disruption of these proteins, resulting in...

A novel compound heterozygous mutation in the thyroglobulin gene resulting in congenital goitrous hypothyroidism with high serum triiodothyronine levels Abstract Thyroglobulin abnormality is a rare cause of congenital hypothyroidism and only a limited number of mutations in the thyroglobulin gene have been reported. We analyzed the thyroglobulin gene in a patient with congenital goitrous hypothyroidism. This girl was identified with hyperthyrotropinemia in a neonatal mass-screening test. The patient had goiter, and her body weight gain was poor. Distal femoral epiphysis was absent on roentgenography. Her serum thyroxine level was low; however, her triiodothyronine level was high. Autoantibodies against triiodothyronine, thyroid peroxidase, and thyroglobulin were all negative. Her serum thyroglobulin level was undetectable. The thyroglobulin gene from the genomic DNA of the patient was analyzed by direct sequencing. Two novel heterozygous missense mutations, Cys1897Tyr (exon 31) and Arg2336Gln (exon 40), were found in the patient. The former mutation was derived from her mother, suggesting a compound heterozygous state. Normal triiodothyronine and low thyroxine concentrations are often observed in patients with thyroglobulin gene mutations. We considered that some patients with thyroglobulin abnormality might have high triiodothyronine levels. In cases of congenital goitrous hypothyroidism with normalto-high triiodothyronine levels and low serum thyroglobulin levels, thyroglobulin abnormality should be considered.

Bartter syndrome is a genetic disorder with hypokalemic metabolic alkalosis and is classified into five types. Type IV Bartter syndrome is a type of neonatal Bartter syndrome with sensorineural deafness and has been recently shown to be caused by mutations in the BSND gene. Owing to the rarity of this disease, only a limited number of mutations have been reported. We analyzed the BSND gene in a patient with type IV Bartter syndrome. The patient was delivered at 37 weeks, with normal body weight, and his neonatal course was uneventful. He was examined for developmental delay and polyuria at age 1 year 8 months and was found to have hypokalemia, metabolic alkalosis, hyperreninemic hyperaldosteronism, and sensorineural deafness. He developed end-stage renal failure at age 15 years, and renal transplantation was performed. We identified compound heterozygous mutations (Q32X and G47R) in the BSND gene. Each mutation was inherited from the parents. The Q32X mutation is a novel mutation and the first nonsense mutation identified in this gene. The mild perinatal clinical features of the patient were similar to those of a patient reported with a homozygous G47R mutation. However, the severity of renal failure suggested that factors other than this gene might affect the manifestation of renal abnormalities.

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Mutations in hepatocyte nuclear factor-1b (HNF-1b) lead to type 5 maturity-onset diabetes of the young (MODY5). Moreover, mutations in the HNF-1b gene might cause multiorgan abnormalities including renal diseases, genital malformations, and abnormal liver function. The objective of this study was to investigate the molecular mechanism of diabetes mellitus, intrauterine growth retardation, and cholestasis observed in MODY5 patients. We analyzed the transactivity of wild-type and three mutant HNF-1b on native human insulin, IGF-I, and multidrug resistance protein 2 (MRP2) promoters in combination with HNF-1a, using a reporter-assay system in transiently transfected mammalian cells. In the human insulin gene promoter, we found that the cooperation of HNF-1a and HNF-1b is prominent. Absence of this cooperation was observed in all of the HNF-1b mutants. In the human IGF-I and MRP2 promoters, we found that the HNF-1b His153Asn (H153N) mutant had a mutant-specific repressive effect on both HNF-1a and wild-type HNF-1b transactivity. Absence of the cooperation of HNF-1b mutants with HNF-1a in the human insulin gene promoter might be one cause of defective insulin secretion. The H153N mutantspecific repression of HNF-1a and HNF-1b transactivity in human IGF-I and MRP2 promoters might explain the casespecific clinical features of growth retardation and cholestasis observed only in early infancy. We found differential property of HNF-1a/HNF-1b activity and the effect of HNF-1b mutants by the promoters. We consider that analyses of HNF1b mutants on the intended human native promoters in combination with HNF-1a may be useful in investigating the molecular mechanisms of the various features in MODY5.