Mechanisms of PiT2-loop7 Missense Mutations Induced Pi Dyshomeostasis / 神经科学通报·英文版

PiT2 is an inorganic phosphate (Pi) transporter whose mutations are linked to primary familial brain calcification (PFBC). PiT2 mainly consists of two ProDom (PD) domains and a large intracellular loop region (loop7). The PD domains are crucial for the Pi transport, but the role of PiT2-loop7 remains unclear. In PFBC patients, mutations in PiT2-loop7 are mainly nonsense or frameshift mutations that probably cause PFBC due to C-PD1131 deletion. To date, six missense mutations have been identified in PiT2-loop7; however, the mechanisms by which these mutations cause PFBC are poorly understood. Here, we found that the p.T390A and p.S434W mutations in PiT2-loop7 decreased the Pi transport activity and cell surface levels of PiT2. Furthermore, we showed that these two mutations attenuated its membrane localization by affecting adenosine monophosphate-activated protein kinase (AMPK)- or protein kinase B (AKT)-mediated PiT2 phosphorylation. In contrast, the p.S121C and p.S601W mutations in the PD domains did not affect PiT2 phosphorylation but rather impaired its substrate-binding abilities. These results suggested that missense mutations in PiT2-loop7 can cause Pi dyshomeostasis by affecting the phosphorylation-regulated cell-surface localization of PiT2. This study helps understand the pathogenesis of PFBC caused by PiT2-loop7 missense mutations and indicates that increasing the phosphorylation levels of PiT2-loop7 could be a promising strategy for developing PFBC therapies.

Analysis of USH2A gene mutation in a Chinese family affected with Usher syndrome / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To investigate the disease-causing mutation in a Chinese family affected with Usher syndrome type II.</p><p><b>METHODS</b>All of the 11 members from the family underwent comprehensive ophthalmologic examination and hearing test, and their genomic DNA were isolated from venous leukocytes. PCR and direct sequencing of USH2A gene were performed for the proband. Wild type and mutant type minigene vectors containing exon 42, intron 42 and exon 43 of the USH2A gene were constructed and transfected into Hela cells by lipofectamine reagent. Reverse transcription (RT)-PCR was carried out to verify the splicing of the minigenes.</p><p><b>RESULTS</b>Pedigree analysis and clinical diagnosis indicated that the patients have suffered from autosomal recessive Usher syndrome type II. DNA sequencing has detected a homozygous c.8559-2A>G mutation of the USH2A gene in the proband, which has co-segregated with the disease in the family. The mutation has affected a conserved splice site in intron 42, which has led to inactivation of the splice site. Minigene experiment has confirmed the retaining of intron 42 in mature mRNA.</p><p><b>CONCLUSION</b>The c.8559-2A>G mutation in the USH2A gene probably underlies the Usher syndrome type II in this family. The splice site mutation has resulted in abnormal splicing of USH2A pre-mRNA.</p>

Identification of a new lamin A/C mutation in a chinese family affected with atrioventricular block as the prominent phenotype / 华中科技大学学报（医学）（英德文版）

Even though mutations in LMNA have been reported in patients with typical dilated cardiomyopathy (DCM) and atrioventricular block (AVB) previously, the purpose of this study was to disclose this novel genetic abnormality in one Chinese family with the atypical phenotype of progressive AVB followed by DCM with normal QRS interval. Genome-wide linkage analysis mapped the AVB gene in this family to a marker at chromosome 1q21.2, where the LMNA gene was located. Direct DNA sequence analysis revealed a heterozygous G to A transition at nucleotide 244 in exon 1 of LMNA, which resulted in an E82K mutation. The E82K mutation co-segregated with all affected individuals in the family, and was not present in 200 normal controls. Further clinical evaluation of mutation carriers showed that 5 of 6 AVB patients exhibited mild DCM with a late onset of age in the fourth and fifth decades. Ejection fractions were documented in 5 patients with DCM, but 4 showed a normal value of [Symbol: see text]50%. Echocardiography showed that atrial dilatation occurred earlier than ventricular dilatation in the patients. This study suggests that progressive AVB with normal QRS interval and accompanying DCM at later stages may represent a distinct type of DCM. The molecular mechanism by which the E82K mutation causes AVB as the prominent phenotype in DCM may be a focus of future studies.

Two variants in MYOC and CYP1B1 genes in a Chinese family with primary angle-closure glaucoma / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To describe the clinical and genetic characteristics of a Chinese family with primary angle-closure glaucoma (PACG).</p><p><b>METHODS</b>Linkage analysis and DNA sequencing as well as single strand conformation polymorphism (SSCP) analysis were performed to identify the disease-causing mutations.</p><p><b>RESULTS</b>The Arg46Stop mutation in MYOC gene and Leu432Val in CYP1B1 gene were identified in all patients. The digenic alterations have not been identified in any same Chinese control individuals.</p><p><b>CONCLUSION</b>Author identified digenic mutations, Arg46Stop in MYOC gene and Leu432Val in CYP1B1 gene, in a Chinese PACG family. Author's studies suggest a possible role of MYOC and CYP1B1 in the development of PACG and support the hypothesis that PAOG and PACG may have common origin across multiple glaucoma phenotypes.</p>

A novel COL4A5 splicing mutation causing Alport syndrome in a Chinese family / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify the pathogenic mutation in a Chinese family with Alport syndrome.</p><p><b>METHODS</b>Blood samples were collected from the members of the family. Direct DNA sequence analysis of the entire coding region and exon-intron boundaries of the COL4A5 gene was performed, and restriction fragment length polymorphism (RFLP) analysis was used to confirm the sequencing results and to test the mutation in all the family members and 200 controls.</p><p><b>RESULTS</b>A novel splicing mutation of c.1517-1G to T in the COL4A5 gene was identified in all patients in the family. RFLP analysis did not detect this mutation in all the unaffected family members and the 200 controls.</p><p><b>CONCLUSION</b>This data revealed a novel splicing mutation of c.1517-1G to T in the COL4A5 gene causing Alport syndrome in a Chinese family. Author's study enriched the spectrum of COL4A5 mutation associated with Alport syndrome.</p>

Genetic polymorphisms of brain-derived neurotrophic factor and sporadic Parkinson disease / 中国组织工程研究

BACKGROUND: Brain-derived neurotrophic factor(BDNF) is a potent dopaminergic neurotrophin. The major pathological change in Parkinson disease(PD) is the degeneration and death of dopaminergic neurons in the substantia nigra pars compacta. There is a possibility that the onset of PD is associated with BDNF genetic polymorphisms.OBJECTIVE: To investigate the relationship between BDNF genetic polymorphisms and sporadic Parkinson disease(SPD) in Chinese population with the expectation of offering some genetic data for the primary rehabilitation and prevention of the disease.DESIGN: Explorative study based on DNA samples of SPD patients as study group and DNA samples of healthy population as control group.SETTING: Neurological Department of Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, and Human Genome Center of Huazhong University of Science and Technology.PARTICIPANTS: Subjects included DNA samples of 85 SPD patients(study group, Han population, living in Huazhong area for a long term) offered by Department of Neurology of Wuhan Union Hospital and DNA samples of health persons(control group, Han population, living in Huazhong area for a long term) offered by Human Genome Center of Huazhong University of Science and Technology.METHODS: The genotype of healthy controls and SPD patients was analyzed with the polymerase chain reaction-restriction fragment length polymorphism technique (PCR-RFLP).MAIN OUTCOME MEASURES: Genotypes and alleles of the two polymorphisms: G196A and C270T of the two groups.RESULTS: G/A genotype was dominant in both SPD patients and control group with frequencies of 50.6% and 52.0% respectively. The C/C genotype occurred with the frequency of 100% in both groups. There were no significant differences in genotype and allele frequencies of G196A and C270T between SPD and control group( P ＞ 0. 05).CONCLUSION: No association existed between BDNF genetic polymorphisms and the onset of SPD in Chinese Han population of Huazhong area.

Two novel mutations of the retinitis pigmentosa GTPase regulator gene in two Chinese families with X-linked retinitis pigmentosa / 中华医学杂志(英文版)

<p><b>OBJECTIVE</b>To detect mutations of the retinitis pigmentosa GTPase regulator (RPGR) gene in two Chinese X-linked retinitis pigmentosa families.</p><p><b>METHODS</b>Fragments of exons 1-19 of the RPGR gene were amplified with intronic primers, using genomic DNA as template. The polymerase chain reaction (PCR) products were analysed by single-strand conformation polymorphism (SSCP) and direct sequencing. Mutations were identified by comparing DNA sequences of the patients with those of the normal controls.</p><p><b>RESULTS</b>Two novel mutations, c1536delC and E332X, were identified in exons 12 and 9 of the RPGR gene in both families. Each mutation was the first mutation found in their respective exons. Both mutations were predicted to cause premature termination, which resulted in truncated proteins without normal functions of the RPGR products.</p><p><b>CONCLUSIONS</b>Both mutations are the genetic basis of the pathogenesis in the respective families. Our data might be helpful in analysing the function of the RPGR protein.</p>