Expression and variability of lipid metabolism genes in intracranial aneurysm

The objective of this study was to investigate the association between mRNA expression and single nucleotide polymorphisms (SNPs) of the ATP-binding cassette transporter (ABCA1) gene, apolipoprotein A1 (APOA1) gene, low-density lipoprotein (LDLR) gene and RNA gene located in the CDKN2B-CDKN2A cluster (CDKN2B-AS1) involved in lipid metabolism and the occurrence of intracranial aneurysm (IA). Fifty three IA patients, and 27 controls (IA-free) were enrolled in this study and were genotyped for seven single nucleotide polymorphisms. Increased expression of the LDLR gene in IA patients was observed. The A/G genotype and the A allele of the c. -113G>A polymorphism of the APOA1 gene were associated with increased occurrence of IA (ORs 12.36 and 14.14, respectively), while the G/G genotype and G allele showed the opposite tendency (ORs 0.06 and 0.07, respectively). We also detected that the A/A-G/A combined genotype of the c. -113G>A - APOA1 and g.46859A>G - LDLR SNPs was associated with a decreased occurrence of IA. Moreover, the A/G-G/G combined genotype of the c.656G>A - ABCA1 and c. -113G>A - APOA1 was associated with a decreased occurrence of IA. The results of our study suggest the association between expression and variability of lipid metabolism genes and occurrence of IA.

GADD45A and EPB41 as tumor suppressor genes in meningioma pathogenesis

Deletions of 1p occur in approximately 30% of meningiomas. Based on loss of heterozygosity (LOH) analysis, two regions on 1p have been suspected to be carriers of tumor suppressor genes. We chose the GADD45A and EPB41 genes as tumor suppressor candidates based on their function and chromosomal localization. We analyzed 19 cases of meningioma with LOH of 1p by means of sequencing of the GADD45A gene and Western blotting of the GADD45a protein. Twenty cases of meningioma without 1p LOH were also analyzed by Western blotting to find out if changes of the GADD45a protein expression occurred. Nineteen samples with 1p LOH (12 grade I; 7 grade II, WHO classification) and 20 samples without 1p LOH (18 grade I; 2 grade II) were also analyzed by means of real-time polymerase chain reaction to find abnormalities in EPB41 mRNA levels in meningioma. LOH analysis was performed using seven microsatellite markers: D1S508 (1p36.2), D1S199 (1p36.1) D1S2734 (1p36.1), D1S2720 (1p34), D1S197 (1p32), D1S162 (1p32), D1S429 (1p11). LOH analysis confirmed previously described localization of putative tumor suppressor genes on 1p and involvement in meningioma pathogenesis (1p36 and 1p32). The open reading frame of GADD45A and intron splicing sites showed neither mutations nor polymorphisms. GADD45a protein molecular weight and expression level were unaltered in meningiomas with and without 1p LOH. We conclude that the GADD45A gene is not involved in meningioma tumorigenesis. EPB41 gene expression was unchanged in all analyzed meningiomas. This suggests that involvement of the EPB41 gene (4.1R protein) in meningioma pathogenesis should be reconsidered.

Thyrotropin (TSH) receptor autoantibodies do not appear to bind to the TSH receptor produced in an in vitro transcription/translation system

An in vitro transcription/translation (TnT) system was used to produce 35S-labeled full-length TSH receptor (TSHR) and TSHR extracellular domain (TSHRex). The interaction of the labeled proteins with TSHR autoantibodies in Graves' sera was then studied using an immunoprecipitation assay. In the assay, 35S-labeled TSHR or TSHRex were incubated with test sera, and any immune complexes formed were precipitated with protein A-Sepharose (in the case of mouse monoclonal antibodies, antimouse IgG-agarose was used). Rabbit antibodies to the TSHR and a mouse monoclonal antibody precipitated as much as 50% of the 35S-labeled TSHR preparations compared with about 2% for normal rabbit serum and 4% for a control monoclonal antibody. However, none of 34 Graves' sera (TSHR autoantibody levels ranging from 14-95% inhibition of [125I]TSH binding) were able specifically to immunoprecipitate 35S-labeled TSHR or TSHRex. These negative findings were confirmed by analysis of the immunoprecipitates on SDS-PAGE followed by autoradiography. Our results indicate that the TnT system is not useful for producing labeled TSHR preparations that can bind TSHR autoantibodies well. This is in contrast to TnT produced 35S-labeled glutamic acid decarboxylase, thyroid peroxidase, and 21-hydroxylase, which react well with their respective autoantibodies. One main difference between these 3 autoantigens and the TSHR is that the receptor is highly glycosylated, and this extensive glycosylation may be of critical importance for correct folding of the receptor. Consequently, the inability of the TnT system to glycosylate proteins could explain in part why TnT-produced 35S-labeled TSHR and TSHRex do not bind TSHR autoantibodies.