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Glutathione S-transferase theta enzyme activity involved in the metabolism of toxic compounds is absent in approximately 20% of Caucasians due to a homozygous deletion of GSTT1 (*0/0). Because the exact manner of the GSTT1 deletion was unknown, current genotyping of GSTT1 was limited to detect the presence versus complete absence of the gene by a GSTT1-specific polymerase chain reaction (PCR). Thus, heterozygous (*A/0) and homozygous (*A/A) samples could not be discriminated. We have characterized the boundaries of the deletion of the human glutathione S-transferase theta (GSTT1) gene: PCR mapping and sequencing revealed a 54251 bp fragment including GSTT1 to be deleted from chromosome 22, most likely by a homologous recombination event between two highly homologous sequence stretches that flank GSTT1. Based on the knowledge of the GSTT1*0 region, a PCR assay was devised for unambiguous discrimination of homozygously deleted (*0/0), heterozygously (*A/0) and homozygously GSTT1 carrying (*A/A) individuals. Genotyping of 180 samples of a Caucasian population revealed that the deletion consists of one defined allele, whose distribution in the population fits the Hardy-Weinberg equilibrium with observed 20% *0/0, 46% *A/0 and 34% *A/A individuals. The number of GSTT1*A alleles detected by this procedure correlated highly significant with the enzyme activity in erythrocytes. Genotype-phenotype comparisons demonstrated a codominant type of inheritance by a gene-dose effect: samples with two active alleles expressed a statistically significant higher enzymatic activity compared to those with one null allele (P < 0.0001, ANOVA).
Yes, however, all of the SNPs are there for all 40 of GSTM1 and GSTP1 SNPs. 23andMe does not report my GSTT1 as a deletion (they say they don't regularly keep track of deletions), but instead says "no call" for all SNPs. However, I think it's logical that it is probably a deletion. But I sent in a support ticket asking them if it could be.
Me, too. I have rs11550605 TT and rs11550605 is AA. The rest are no call. Sea, Are these the same ones you have?I have a "no call" for 12 out of the 14 snps tested for GSTT1. I've just assumed it's a deletion since it's not uncommon for there to be significant deletions in this gene.
Me, too. I have rs11550605 TT and rs11550605 is AA. The rest are no call. Sea, Are these the same ones you have?
In areas where I have an insertion or deletion, I get an I or D in my report, instead of A,C,G, or T.
I got my results late July (~26th). I just poked into 'browse' to respond to this post, though, so my no-calls were from their website the day I made the post.How long have you had your results?
If you have any SNPs on GSTT1, then you have the gene.I got tested in July 2014 with the V4 chip. I have no call on all except 3 of the SNPs 23andMe shows for GSTT1.
This is weird. Why would this happen? It kinda freaked me out a bit.