Complete or partial loss of the Y chromosome in an unselected cohort of 865 non-vasectomized, azoospermic men

BACKGROUND

Structural abnormalities as well as minor variations of the Y chromosome may cause disorders of sex differentiation or, more frequently, azoospermia. This study aimed to determine the prevalence of loss of Y chromosome material within the spectrum ranging from small microdeletions in the azoospermia factor region (AZF) to complete loss of the Y chromosome in azoospermic men.

RESULTS

Eleven of 865 azoospermic men (1.3%) collected from 1997 to 2022 were found to have a karyotype including a 45,X cell line. Two had a pure 45,X karyotype and nine had a 45,X/46,XY mosaic karyotype. The AZF region, or part of it, was deleted in eight of the nine men with a structural abnormal Y-chromosome. Seven men had a karyotype with a structural abnormal Y chromosome in a non-mosaic form. In addition, Y chromosome microdeletions were found in 34 men with a structural normal Y chromosome. No congenital malformations were detected by echocardiography and ultrasonography of the kidneys of the 11 men with a 45,X mosaic or non-mosaic cell line.

CONCLUSIONS

In men with azoospermia, Y chromosome loss ranging from small microdeletions to complete loss of the Y chromosome was found in 6.1% (53/865). Partial AZFb microdeletions may give a milder testicular phenotype compared to complete AZFb microdeletions.

Combined score of Y chromosome loss and T-cell infiltration improves UICC based stratification of esophageal adenocarcinoma

Background

Staging, especially clinical lymph node staging in esophageal adenocarcinoma has only moderate sensitivity and specificity. Therefore, we evaluated combined molecular markers to predict prognosis.

Patients and methods

890 tumor tissue samples were obtained from patients who underwent surgery for esophageal adenocarcinoma with curative intent. These were stained by tissue micro array for 48 markers which are associated with tumorigenesis and correlated with clinical data (TNM-staging, overall survival) by multivariate Cox regression.

Results

Two markers (preserved Y chromosome and high grade of (CD3+) T-cell infiltration) were found to be significantly and independently associated with better overall survival. We formed a score (called CY score) from the two markers. The more markers are positive and thus the higher the score (ranging from 0 to 2), the better the overall survival, independently of UICC. Moreover, we developed a combination score of the UICC and CY score based on cluster analysis. Patients with a UICC stage of III with the presence of both traits (CY=2) can be assigned to a better prognosis group (group II), whereas patients with a UICC stage of I without both traits (CY=0) must be assigned to a worse prognosis group (group II). Therefore, patients in stage I with adverse molecular signature might benefit of multimodal therapy.

Conclusion

In summary, the CY score adds prognostic information to the UICC stage based on tumor biology in esophageal adenocarcinoma and warrants further evaluations in independent clinical cohorts.

Somatic loss of the Y chromosome is associated with arsenic exposure among Bangladeshi men

BACKGROUND

Arsenic exposure increases the risk of several cancers in humans and contributes to genomic instability. Somatic loss of the Y chromosome (LoY) is a potential biomarker of genomic instability and cancer risk. Smoking is associated with LoY, but few other carcinogens have been investigated. We tested the cross-sectional association between arsenic exposure and LoY in leukocytes among genotyped Bangladeshi men (age 20-70 years) from the Health Effects of Arsenic Longitudinal Study.

METHODS

We extracted the median of logR-ratios from probes on the Y chromosome (mLRR-chrY) from genotyping arrays (n = 1364) and estimated the percentage of cells with LoY (% LoY) from mLRR-chrY. We evaluated the association between arsenic exposure (measured in drinking water and urine) and LoY using multivariable linear and logistic regression models. The association between LoY and incident arsenic-induced skin lesions was also examined.

RESULTS

Ten percent of genotyped men had LoY in at least 5% of cells and % LoY increased with age. Among men randomly selected for genotyping (n = 778), higher arsenic in drinking water, arsenic consumed and urinary arsenic were associated with increased % LoY (P = 0.006, P = 0.06 and P = 0.13, respectively). LoY was associated with increased risk of incident skin lesions (P = 0.008).

CONCLUSION

Arsenic exposure was associated with increased LoY, providing additional evidence that arsenic contributes to genomic instability. LoY was associated with developing skin lesions, a risk factor for cancer, suggesting that LoY may be a biomarker of susceptibility in arsenic-exposed populations. The effect of arsenic on somatic events should be further explored in cancer-prone tissue types.

Meiotic Executioner Genes Protect the Y from Extinction

The Y has been described as a wimpy degraded relic of the X, with imminent demise should it lose sex-determining function. Why then has it persisted in almost all mammals? Here we present a novel mechanistic explanation for its evolutionary perseverance: the persistent Y hypothesis. The Y chromosome bears genes that act as their own judge, jury, and executioner in the tightly regulated meiotic surveillance pathways. These executioners are crucial for successful meiosis, yet need to be silenced during the meiotic sex chromosome inactivation window, otherwise germ cells die. Only rare transposition events to the X, where they remain subject to obligate meiotic silencing, are heritable, posing strong evolutionary constraint for the Y chromosome to persist.

Y Chromosome Loss is a Frequent Event in Barrett's Adenocarcinoma and Associated with Poor Outcome

Background: The loss of the Y chromosome in various malignant diseases has been described previously. There are no reliable information on the actual frequency, significance and homogeneity of Y chromosome loss (LoY) in esophageal adenocarcinoma (EAC). Methods: 400 male EAC including lymph-node metastases were analyzed with commercially available Y chromosome specific fluorescence in-situ probes. The results were correlated with molecular and immunohistochemical markers and clinicopathological aspects. Results: The entire cohort (n = 400) showed a singular LoY of one chromosome arm in 1.0% (q-arm) and 2.8% (p-arm), complete LoY in 52.5%. LoY was strongly associated with shortened overall-survival (OS). Patients with preserved Y chromosome had a median OS of 58.8 months, patients with LoY an OS of 19.4 months (p < 0.001). Multivariate analysis showed LoY as an independent prognostic marker with a hazard ratio of 1.835 (95% CI 1.233–2.725). LoY correlated with TP53 mutations (p = 0.003), KRAS amplification (p = 0.004), loss of ARID1a (p = 0.045) and presence of LAG3 (p = 0.018). Conclusions: Loss of the Y chromosome is a very common phenomenon in EAC. The LoY is heterogeneously distributed within the tumor, but corresponding lymph node metastases frequently show homogeneous LoY, indicating a selection and metastasizing advantage with poor prognosis. To date, the male predominance of EAC (7–9:1) is unclear, so genetic explanatory models are favored. The LoY in EAC may be biologically and functionally relevant and additional genomic or functional analyses are needed.

Long-Term Fragility of Y Chromosomes Is Dominated by Short-Term Resolution of Sexual Antagonism

The evolution of heteromorphic sex chromosomes has fascinated biologists, inspiring theoretical models, experimental studies, and studies of genome structure. This work has produced a clear model, in which heteromorphic sex chromosomes result from repeated fixations of inversions (or other recombination suppression mechanisms) that tether sexually antagonistic alleles to sex-determining regions, followed by the degeneration of these regions induced by the lack of sex chromosome recombination in the heterogametic sex. However, current models do not predict if inversions are expected to preferentially accumulate on one sex-chromosome or another, and do not address if inversions can accumulate even when they cause difficulties in pairing between heteromorphic chromosomes in the heterogametic sex increasing aneuploidy or meiotic arrest. To address these questions, we developed a population genetic model in which the sex chromosome aneuploidy rate is elevated when males carry an inversion on either the X or Y chromosome. We show that inversions fix more easily when male-beneficial alleles are dominant, and that inversions on the Y chromosome fix with lower selection coefficients than comparable X chromosome inversions. We further show that sex-chromosome inversions can often invade and fix despite causing a substantial increase in the risk of aneuploidy. As sexual antagonism can lead to the fixation of inversions that increase sex chromosomes aneuploidy (which underlies genetic diseases including Klinefelter and Turner syndrome in humans) selection could subsequently favor diverse mechanisms to reduce aneuploidy-including alternative meiotic mechanisms, translocations to, and fusions with, the sex chromosomes, and sex chromosome turnover.