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Yao-Hua Zhang

Publications and source records attributed to Yao-Hua Zhang.

12 recordsLinked to original sources
PubMed2007

Deletion mapping in Xp21 for patients with complex glycerol kinase deficiency using SNP mapping arrays.

Infantile or complex glycerol kinase deficiency (cGKD) is a contiguous gene deletion syndrome caused by a loss of GK (MIM# 300474), along with its neighboring genes, Duchenne muscular dystrophy (DMD; MIM# 300377) and/or Nuclear Receptor Subfamily 0, Group B, Member 1 (NR0B1; MIM# 300473). Patients with cGKD present with glyceroluria and hyperglycerolemia in association with DMD and/or adrenal hypoplasia congenita (AHC). The purpose of these investigations was to determine whether the Affymetrix GeneChip Mapping Array (SNP chip) could be utilized to detect and map breakpoints in patients with cGKD. Genomic DNAs from several primary lymphoblastoid cell lines from patients with cGKD were analyzed on the Affymetrix platform. The Affymetrix SNP chip is a high-density oligonucleotide array that allows a standardized, parallel interrogation of thousands of SNPs across the entire genome (except for the Y chromosome). Analysis of the array features' hybridization intensities enabled clear delineation of the patient deletions with a high degree of confidence. Many of these patient deletions had been mapped by PCR and their breakpoints confirmed by sequencing. This study demonstrates the utility of the Affymetrix Mapping GeneChips for molecular cytogenetic analysis, beyond the SNP genotyping for which the arrays were initially designed. With one out of 160 live births (approximately 25,000 U.S. neonates annually) reported to have cytogenetic disorders, we envision a significant need for such a standardized platform to carry out rapid, high-throughput, genomic analyses for molecular cytogenetics applications.

Cells, Cultured↗
PubMed2006

Dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome, gene 1 (DAX1) (NR0B1) and small heterodimer partner (SHP) (NR0B2) form homodimers individually, as well as DAX1-SHP heterodimers.

Dosage-sensitive sex reversal adrenal hypoplasia congenita critical region on the X chromosome, gene 1 (DAX1) (NR0B1), and small heterodimer partner (SHP) (NR0B2) are atypical nuclear receptor superfamily members that function primarily as corepressors through heterodimeric interactions with other nuclear receptors. Mutations in DAX1 cause adrenal hypoplasia congenita, and mutations in SHP lead to mild obesity and insulin resistance, but the mechanisms are unclear. We investigated the existence and subcellular localization of DAX1 and SHP homodimers and the dynamics of homodimerization. We demonstrated DAX1 homodimerization in the nucleus and cytoplasm, and dissociation of DAX1 homodimers upon heterodimerization with steroidogenic factor 1 (SF1) or ligand-activated estrogen receptor-alpha (ERalpha). DAX1 homodimerization involved an interaction between its amino and carboxy termini involving its LXXLL motifs and activation function (AF)-2 domain. We observed SHP homodimerization in the nucleus of mammalian cells and showed dissociation of SHP homodimers upon heterodimerization with ligand-activated ERalpha. We observed DAX1-SHP heterodimerization in the nucleus of mammalian cells and demonstrated the involvement of the LXXLL motifs and AF-2 domain of DAX1 in this interaction. We further demonstrate heterodimerization of DAX1 with its alternatively spliced isoform, DAX1A. This is the first evidence of homodimerization of individual members of the unusual NR0B nuclear receptor family and heterodimerization between its members. Our results suggest that DAX1 forms antiparallel homodimers through the LXXLL motifs and AF-2 domain. These homodimers may function as holding reservoirs in the absence of heterodimeric partners. The formation of DAX1 and SHP homodimers and DAX1-SHP and DAX1-DAX1A heterodimers suggests the possibility of novel functions independent of their coregulator roles, suggesting additional complexity in the molecular mechanisms of DAX1 and SHP action.

Amino Acid Motifs↗
PubMed2006

A familial missense mutation in the hinge region of DAX1 associated with late-onset AHC in a prepubertal female.

Mutations in the DAX1 (Dosage-sensitive sex reversal-Adrenal hypoplasia congenita (AHC) critical region on the X chromosome gene 1; NR0B1) cause X-linked AHC, a disease characterized by primary adrenal failure in infancy and hypogonadotropic hypogonadism. All known missense mutations impair DAX1 repression of steroidogenic factor 1 (SF1) transactivation and have been localized to the putative ligand binding domain. Here, an asymptomatic father and his late-onset AHC daughter were both shown to share a novel DAX1 mutation (C200W), the first missense mutation identified in the hinge region of DAX1. Using immunohistochemistry we demonstrate that the sub-cellular localization of the C200W mutant DAX1 protein is shifted from the nucleus to the cytoplasm. The disturbed localization of the C200W mutant in transfected cells correlates with impaired transcriptional repression activity. The import defect is relatively mild, retaining 80% of wild-type activity, which may explain the unusually mild phenotype. Import of DAX1 into the nucleus involves a direct interaction with SF1. In vitro assays demonstrate that the C200W mutant retains the ability to functionally interact with SF1, which suggests that SF1-independent interactions of DAX1 could be responsible for the import defect.

Active Transport, Cell Nucleus↗
PubMed2006

Asymptomatic isolated human glycerol kinase deficiency associated with splice-site mutations and nonsense-mediated decay of mutant RNA.

Isolated glycerol kinase deficiency (GKD) is an X-linked inborn error of metabolism that is either symptomatic or asymptomatic. GKD is due to deletions of, or mutations within, the GK gene, and there is no genotype-phenotype correlation. We identified three patients with asymptomatic GKD, determined that they had GK splice-site mutations, and studied the stability of their GK mRNA to understand the molecular mechanism of the GKD. All three patient mutations caused a frameshift and introduction of a premature stop codon. A fourth patient had an Alu insertion in intron 4 that led to alternative splicing. To study the effect of splice-site mutations on RNA species, we performed reverse transcriptase PCR and found only normal-sized products for all patients. Incubation with anisomycin to block nonsense-mediated decay (NMD), revealed two RNA species for each individual. Sequence analysis revealed that the larger bands represented the wild-type GK RNA and smaller bands represented mutant misspliced RNA, suggesting that the abnormal RNA species were targeted by NMD. Normal RNA species observed in each patient are likely responsible for their mild phenotypes. We speculate that influences on RNA processing and protein stability represent modifiers of the GKD phenotype.

Aged↗
PubMed2005

Human and murine glycerol kinase: influence of exon 18 alternative splicing on function.

Glycerol kinase (GK) is a key enzyme in glycerol metabolism with two alternatively spliced forms-one with an 87bp insertion corresponding to exon 18 (GK+EX18), and one lacking exon 18 (GK-EX18). We report the expression of GK+/-EX18 in various tissues and cell lines, as well as their enzymatic characteristics and subcellular localization. RT-PCR revealed differential expression in tissues and cell lines. Northern blot analysis revealed that both forms of the murine ortholog, Gyk, were highly expressed in murine heart and increased during embryonic development. K(m) values for glycerol for GK+/-EX18 were not significantly different, although GK-EX18 had a higher V(max) for glycerol. GK-EX18 had a lower K(m) and V(max) for ATP than GK+EX18. Immunofluorescence experiments showed that GK+EX18 co-localized to the mitochondria and the perinuclear region while GK-EX18 had a diffuse expression pattern. These data suggest specific and divergent roles for GK+EX18 and GK-EX18 in cellular metabolism and development.

Alternative Splicing↗
PubMed2005

Molecular genetic confirmatory testing from newborn screening samples for the common African-American, Asian Indian, Southeast Asian, and Chinese beta-thalassemia mutations.

beta-Thalassemia is a serious health problem in the United States, especially in California, due to increased Asian immigration. Neonatal screening by using high-performance liquid chromatography (HPLC) or isoelectric focusing (IEF) may lead to confusion due to interactions of various hemoglobinopathies with beta-thalassemia. Our purpose was to develop single-tube multiplexed PCR assays using original neonatal screening specimens to identify the mutations responsible for beta-thalassemia in order to expedite diagnostic confirmation. Primers were designed for two to six common ethnic-specific mutations using the amplification refractory mutation system (ARMS). This multiplex ARMS approach was standardized using DNA samples with known mutations for beta-thalassemia in those of Asian (Southeast Asian, Chinese, and Asian Indian) and African-American descent. Specimens from African-American neonates were tested for two mutations (-88 and -29); Asian Indians for five mutations (IVSI-1, IVSI-5, codons (Cd) 41/42, Cd 8/9, and 619-bp deletion); Chinese, Taiwanese, and Southeast Asians for seven mutations (Cd 41/42, Cd 17, -28, IVSII-654, Cd 71/72, IVSI-5, and IVSI-1). We identified each of these beta-thalassemia mutations in multiplexed ARMS from positive control samples. We tested 25 anonymized dried blood specimens from neonates who had been diagnosed with beta-thalassemia and who also belonged to these ethnic groups. We detected a mutation specific to the neonate's ethnic group using the ARMS approach in nearly all specimens, and the results were confirmed by sequencing. Multiplexed ARMS for ethnic-specific beta-thalassemia mutations from the original newborn screening dried blood specimens is a rapid and efficient approach for diagnostic confirmation.

Asian People↗
PubMed2004

Rapid, species-specific detection of uropathogen 16S rDNA and rRNA at ambient temperature by dot-blot hybridization and an electrochemical sensor array.

Development of rapid molecular approaches for pathogen detection is key to improving treatment of infectious diseases. For this study, the kinetics and temperature-dependence of DNA probe hybridization to uropathogen species-specific sequences were examined. A set of oligonucleotide probes were designed based on variable regions of the 16S gene of the Escherichia coli, Proteus mirabilis, Klebsiella oxytoca, and Pseudomonas aeruginosa. A universal bacterial probe and probes-specific for gram-positive and gram-negative organisms were also included. The oligonucleotide probes discriminated among 16S genes derived from 11 different species of uropathogenic bacteria applied to nylon membranes in a dot-blot format. Significant binding of oligonucleotide probes to target DNA and removal of nonspecific binding by membrane washing could both be achieved rapidly, requiring as little as 10 min. An oligonucleotide probe from the same species-specific region of the E. coli 16S gene was used as a capture probe in a novel electrochemical 16-sensor array based on microfabrication technology. Sequence-specific hybridization of target uropathogen 16S rDNA was detected through horseradish peroxidase acting as an electrochemical transducer via a second, detector probe. The sensor array demonstrated rapid, species-specific hybridization in a time course consistent with the rapid kinetics of the dot-blot hybridization studies. As in the dot-blot hybridization studies, species-specific detection of bacterial nucleic acids using the sensor array approach was demonstrated both at 65 degrees C and at room temperature. These results demonstrate that molecular hybridization approaches can be adapted to rapid, room temperature conditions ideal for an electrochemical sensor array platform.

Bacteria↗
PubMed2004

IL1RAPL1 is associated with mental retardation in patients with complex glycerol kinase deficiency who have deletions extending telomeric of DAX1.

IL1RAPL1 (interleukin-1 receptor accessory protein-like, gene 1) has recently been shown to be mutated in patients with X-linked mental retardation. Clinical experience has suggested that patients with the contiguous gene syndrome, complex glycerol kinase deficiency (cGKD), will have mental retardation (MR) if they have deletions extending from the GK gene into the DMD gene and/or involving a significant extension telomeric from DAX1. We examined cell lines from patients with cGKD whose clinical features would be informative and would allow us to determine if IL1RAPL1 deletions can help to explain the MR in patients with deletions extending telomeric from DAX1. Our results showed that nearly all patients with deletions involving DAX1, but not DMD, had MR if IL1RAPL1 was deleted. If ILIRAPLI and DMD were intact, the patients with DAX1 deletions only rarely had normal development. Deletions in DNA from patients with cGKD who exhibited MR and had normal IL1RAPL1 all involved the GK and DMD genes. Our data are consistent with the association of IL1RAPL1 gene deletion and MR in the majority of patients with cGKD and deletions extending telomeric from DAX1.

Adrenal Glands↗
PubMed2004

NR0B1A: an alternatively spliced form of NR0B1.

The orphan nuclear receptor DAX1 (dosage-sensitive sex reversal-AHC critical region on the X chromosome gene 1), encoded by the NR0B1 gene, plays important roles in the development of the hypothalamic-pituitary-adrenal/gonadal (HPAG) axis as well as in sex determination. Mutations in NR0B1 cause the X-linked cytomegalic form of adrenal hypoplasia congenita (AHC), and associated hypogonadotropic hypogonadism (HH). Over-expression of NR0B1 results in sex reversal in mice and duplication of the 160kb DSS locus in human patients results in a sex-reversed phenotype (XY females). The purpose of these investigations was to determine if alternatively spliced forms of NR0B1 existed. Analysis of expressed sequence tag data predicted a truncated isoform of DAX1. We confirmed the presence of an alternatively spliced form of NR0B1, which we will refer to as NR0B1A, by reverse transcriptase-polymerase chain reaction (RT-PCR), and will refer to the deduced protein isoform as DAX1A. Sequencing of the NR0B1A cDNA revealed slight differences from the recently described splice form, DAX1alpha. NR0B1A is encoded by NR0B1 exon 1 and exon 2A located within the 3385 nt intron between NR0B1 exons 1 and 2. Exon 2A includes 35 nt of coding sequence. NR0B1A encodes a deduced protein sequence, DAX1A, of 400 amino acids compared with 470 amino acids for DAX1. RT-PCR detected expression of NR0B1A in adrenal gland, testis, ovary, and pancreas. The identification of NR0B1A and the deduced DAX1A requires reinterpretation of many previous experiments involving expression and knockout of NR0B1 and DAX1.

Adrenal Cortex↗
PubMed2003

DNA diagnosis confirms hemoglobin deletion in newborn screen follow-up.

Molecular genetic confirmatory testing with polymerase chain reaction amplification is integral to neonatal hemoglobinopathy screening programs. In this study, we demonstrate applicability of polymerase chain reaction-based testing for the common deletions in blacks responsible for hereditary persistence of fetal hemoglobin. This approach will provide rapid diagnostic clarification in newborn screening follow-up.

Alleles↗
PubMed2002

Rapid confirmation of Southeast Asian and Filipino alpha-thalassemia genotypes from newborn screening specimens.

Alpha(+)-thalassemia (-alpha) is prevalent throughout tropical and subtropical regions of world, whereas alpha(0)-thalassemia (--) occurs at higher frequency in Southeast Asia. Homozygosity for the alpha(0)-thalassemia deletion (--/--) is a serious health problem in Southeast Asia and the Philippines and is responsible for the majority of hydrops fetalis in this region. Asian immigration in United States has impacted the demography of genetic disease in U.S. As Asians comprise of 10% of all California births and represent a population at highest risk for alpha(0)-thalassemia, we developed a rapid and efficient PCR approach to detect the common alpha(0)-thalassemia deletions in Southeast Asians and Filipinos using newborn screening specimen.

Asia, Southeastern↗