GA Allele Research Articles

The E-cadherin -347G->GA promoter polymorphism and its effect on transcriptional regulation.

E-cadherin plays a critical role in epithelial cell-cell adhesion and maintenance of tissue architecture. Loss of E-cadherin expression in humans has been associated with cancer, and a number of cancer-related mutations have been identified. Here, we sought to investigate whether the -347G-->GA single nucleotide polymorphism affects the transcriptional activity of the E-cadherin gene. First, we measured the promoter activity of the -347G-->GA polymorphism using a dual luciferase reporter assay and electrophoretic mobility shift assay (EMSA). The dual luciferase reporter assay showed that the GA allele decreased the transcriptional efficiency by 10-fold (P < 0.001) compared with the G allele. Similarly, EMSA revealed that the GA allele had a weak transcription factor binding strength compared with the G allele. We then examined the frequency of this polymorphism in familial gastric cancer (FGC) patients by denaturing high-performance liquid chromatography. We found that the E-cadherin genotype (-347G/GA heterozygous or GA homozygous) was associated with FGC patients (P < 0.05) compared with the G homozygous genotype. Taken together, these results suggest that the GA allele may cause weak transcription factor binding affinity and low transcriptional activity in E-cadherin expression.

At least two mutant alleles of ornithine delta-aminotransferase cause gyrate atrophy of the choroid and retina in Finns.

Gyrate atrophy of the choroid and retina (GA) is an inherited chorioretinal degeneration caused by deficiency of ornithine delta-aminotransferase (OAT; L-ornithine: 2-oxo-acid aminotransferase; EC 2.6.1.13). GA is one of the "Finnish genetic diseases," a group of several rare monogenic disorders that occur with increased frequency in the Finnish population. Using a combination of RNase A protection, genomic cloning, and polymerase chain reaction amplification of genomic DNA, we found one of two missense mutant OAT alleles to be present in each of 16 Finnish GA pedigrees. The first mutation R180T, in which arginine-180 is replaced by threonine, was present in homozygous form in patients from two pedigrees. The second mutation L402P, in which leucine-402 is replaced by proline, was present in homozygous form in patients from 14 pedigrees. Neither mutation was present in 19 Finnish controls. L402P was not present in 18 non-Finnish GA patients but R180T was found in an American GA patient. We constructed full-length mutant cDNAs by amplifying patient cDNA with the polymerase chain reaction and cloning a restriction fragment containing the mutation into an otherwise normal human OAT cDNA. These mutant cDNAs were then expressed in CHO-K1 cells, which lack endogenous OAT. Both R180T and L402P inactivate OAT. These results show molecular heterogeneity in GA alleles even in the Finnish population.

An initiator codon mutation in ornithine-delta-aminotransferase causing gyrate atrophy of the choroid and retina.

Gyrate atrophy of the choroid and retina (GA) is an autosomal recessive chorioretinal degeneration caused by deficiency of the mitochondrial matrix enzyme, ornithine-delta-aminotransferase (OAT). To study the molecular basis of the mutations causing GA, we cloned and sequenced the human OAT cDNA and determined the intron-exon arrangement of the structural gene. Using the cDNA template, we synthesized antisense RNA probes and performed RNase A protection experiments with RNA from four Lebanese GA patients. We found a probe-target mismatch at the 5' end of the first coding exon and amplified this region of the patients' genomic DNA using the polymerase chain reaction. Sequence analysis showed a G----A transition, changing the initiator ATG (methionine) codon to ATA. This mutation segregates with the GA allele in both pedigrees. Initiation of translation at the closest in-frame methionine codon would truncate OAT by 138 amino acids, eliminating the entire mitochondrial leader sequence and 113 amino acids of the mature peptide.

Cross‐Incompatibility in Maize1

SynopsisClassification of F2 and backcross populations between dent‐incompatible and dent‐compatible lines indicated in general that they possessed Gas and ga alleles respectively for incompatibility and compatibility to dent corn pollen. However, some inbreds appeared to possess alleles either differing from the type Gas and ga or possessed modifying genes which altered the dent in compatibility reaction.