Molecular Characterization of the NF2 Gene in Korean Patients with Neurofibromatosis Type 2: A Report of Four Novel Mutations / 대한진단검사의학회지

BACKGROUND: Neurofibromatosis type 2 (NF2) is an autosomal dominant syndrome caused by the NF2 tumor suppressor gene. However, the NF2 mutation characteristics in Korean patients are not sufficiently understood. In this study, we conducted a comprehensive mutational analysis in 7 Korean NF2 patients by performing direct sequencing and gene-dosage assessment. METHODS: We analyzed all exons and flanking regions of NF2 by direct sequencing and screened the deletions or duplications involving NF2 by multiplex ligation-dependent probe amplification. RESULTS: Four novel NF2 mutations, including 2 splice-site mutations (c.364-1G>A and c.886-3C>G), 1 frameshift mutation (c.524delA), and 1 missense mutation (c.397T>C; p.Cys133Arg), were identified in our patients. No large deletion or duplication was identified in our series. Subsequently, we identified an abnormal splicing product by using reverse transcription-PCR and direct sequencing in 2 patients with a novel splice-site mutation. The missense mutation c.397T>C was predicted to have harmful effects on protein function. CONCLUSIONS: The detection rate of NF2 mutations in Korean patients (57%) is similar to those in other populations. Our results provided a greater insight into the mutational spectrum of the NF2 gene in Korean subjects.

Analysis of polymorphisms in the 5'-flanking region of the apolipoprotein(a) [Apo(a)] gene in Thai subjects with coronary artery diseases.

Lipoprotein(a) [Lp(a)] is a complex lipoprotein particle in human plasma. It is composed of apolipoprotein B (Apo B)-100 and apolipoprotein(a) which are linked by a disulfide bond. Plasma levels of the Lp(a) vary greatly (over 1,000 folds) among individuals. Elevated plasma levels of the Lp(a) have been shown to be an independent risk factor for coronary artery diseases (CAD). The level of Lp(a) is controlled by a single gene, the Apo(a) gene, with multiple alleles; each encodes different concentrations of the Lp(a). Previous studies revealed the presence of polymorphisms in the 5'-flanking region (FL) of the Apo(a) gene at 3 positions: G or A (-914), C or T(-49), and G or A (-21), which can be detected by cleavage of PCR-amplified DNA products with TaqI, MaeII and HhaI, respectively. The 5'-FL genotypes of the Apo(a) gene can be classified by the combination of the presence (+) or absence (-) of these restriction sites into 5 types; type A, +++, type B, -++, type C, -+-, type D, --+ and type E, +-+. In the present study, the authors analyzed the 5' FL types of the Apo(a) gene by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) in 100 healthy control subjects, 26 CAD patients with [Lp(a)] < or = 30 mg/dL, and 94 CAD patients with [Lp(a)] > 30 mg/dL. The authors found that the genotype frequencies of the Apo(a) gene were 53, 16, 27 and 4%, for types A, B, C and D respectively in normal healthy controls. In CAD patients with [Lp(a)] < or = 30 mg/dL, the distribution of the genotype frequencies were 53.8, 11.5, 30.8 and 3.9% for types A, B, C and D, respectively. Additionally in CAD patients with [Lp(a)] > 30 mg/dL, the genotype frequencies were 60.6, 11.7, 21.3 and 6.4% for types A, B, C and D, respectively. The present study might shed some light to understand CAD at the molecular level.

The role of tonicity responsive enhancer sites in the transcriptional regulation of human hsp70-2 in response to hypertonic stress

The inducible 70 kDa heat shock proteins (Hsp70) in mice are encoded by two almost identical genes, hsp70.1 and hsp70.3. Studies have found that only hsp70.1 is induced by hypertonic stress while both hsp70.1 and hsp70.3 genes are expressed in response to heat shock stress. It is unclear if the human counterparts, hsp70-2 and hsp70-1, are differentially regulated by heat shock and osmotic stress. This study found that only hsp70-2 was induced by hypertonic stress in human embryonic kidney epithelial cells and fibroblasts, while heat shock stress induced both hsp70-1 and hsp70-2. The human hsp70-2 promoter region contains three TonE (tonicity-responsive enhancer) sites, which were reported to play an important role in the response to hypertonicity. When the reporter plasmids containing different parts of the 5' flanking region of hsp70-2 were transfected into human embryonic kidney epithelial cells or fibroblasts, one TonE site at -135 was found to play a key role in the response to hypertonicity. The inactivation of the TonE site using site-directed mutagenesis led to the complete loss of induction by hypertonicity, which demonstrates the essential role of the TonE site. This suggests that the TonE site and the TonEBP (TonE binding protein) are the major regulators for the cellular response against high osmolarity in human kidney tissue.