A history of the discovery of random x chromosome inactivation in the human female and its significance

Determination of Barr bodies in Transgender Patients in India - A comparative study

Sex determination in forensic medicine is considered one of the first and foremost steps in personal identification. The need for identifying the exact sex of the individual arises when deciding whether a person can exercise certain civil rights reserved for one particular sex, for competing in sex-specific athletic and sports events, legitimacy, divorce, paternity disputes and also to some criminal offenses. Nuclear sexing by Barr body examination can be done using buccal smears to establish the sex of the individual when routine methods fail to disclose the exact gender of the individual.

Aim

To determine and compare the Barr bodies present in exfoliated buccal epithelial cells in males, females and transgender populations using light and fluorescence microscopy.

Materials and Methods

A total of 90 patients were recruited for the study. Group I consisted of 30 female patients. Group II consisted of 30 male patients and group III consisted of 30 transgender patients. The buccal mucosa was then scraped using a wooden spatula and the cells obtained were fixed in 95% ethanol. Two smears per individual were made and stained. One smear was stained with papanicolaou (PAP) stain and the other with Acridine orange and viewed under light microscopy and fluorescent microscopy, respectively.

Results

When PAP stained slides were examined, the percentage of Barr-bodies in females ranged from 3% to 5% and in males it was 0% and in transgenders, it ranged from 0% to 5%. In Acridine orange stained smears, the percentage of Barr bodies in females ranged from 1% to 3% and in males it was 0% and in transgenders, it was 0%. Kruskal-Wallis test to study the relation of Barr body percentage in females, males and transgender subjects demonstrated significant differences between the groups (P < 0.001). Wilcoxon signed rank test was done for pairwise comparison, which showed that the distribution of percentage of positive cells in females are statistically significant from males and transgenders (P < 0. 001).

Conclusion

Nuclear sexing using Barr bodies offers a simple yet effective method for determining the sex of transgender patients which could help them in understanding their gender identity better and diagnose any underlying chromosomal aberration.

X chromosome escapee genes are involved in ischemic sexual dimorphism through epigenetic modification of inflammatory signals

BACKGROUND

Stroke is a sexually dimorphic disease. Previous studies have found that young females are protected against ischemia compared to males, partially due to the protective effect of ovarian hormones, particularly estrogen (E2). However, there are also genetic and epigenetic effects of X chromosome dosage that contribute to stroke sensitivity and neuroinflammation after injury, especially in the aged. Genes that escape from X chromosome inactivation (XCI) contribute to sex-specific phenotypes in many disorders. Kdm5c and kdm6a are X escapee genes that demethylate H3K4me3 and H3K27me3, respectively. We hypothesized that the two demethylases play critical roles in mediating the stroke sensitivity.

METHODS

To identify the X escapee genes involved in stroke, we performed RNA-seq in flow-sorted microglia from aged male and female wild type (WT) mice subjected to middle cerebral artery occlusion (MCAO). The expression of these genes (kdm5c/kdm6a) were confirmed in four core genotypes (FCG) mice and in post-mortem human stroke brains by immunohistochemistry (IHC), Western blot, and RT-PCR. Chromatin immunoprecipitation (ChIP) assays were conducted to detect DNA levels of inflammatory interferon regulatory factor (IRF) 4/5 precipitated by histone H3K4 and H3K27 antibodies. Manipulation of kdm5c/kdm6a expression with siRNA or lentivirus was performed in microglial culture, to determine downstream pathways and examine the regulatory roles in inflammatory cytokine production.

RESULTS

Kdm5c and kdm6a mRNA levels were significantly higher in aged WT female vs. male microglia, and the sex difference also existed in ischemic brains from FCG mice and human stroke patients. The ChIP assay showed the IRF 4/5 had higher binding levels to demethylated H3K4 or H3K27, respectively, in female vs. male ischemic microglia. Knockdown or over expression of kdm5c/kdm6a with siRNA or lentivirus altered the methylation of H3K4 or H3K27 at the IRF4/5 genes, which in turn, impacted the production of inflammatory cytokines.

CONCLUSIONS

The KDM-Histone-IRF pathways are suggested to mediate sex differences in cerebral ischemia. Epigenetic modification of stroke-related genes constitutes an important mechanism underlying the ischemic sexual dimorphism.