ZW sex-chromosome evolution and contagious parthenogenesis in Artemia brine shrimp

Eurasian brine shrimp (genus Artemia) have closely related sexual and asexual lineages of parthenogenetic females, which produce rare males at low frequencies. Although they are known to have ZW chromosomes, these are not well characterized, and it is unclear whether they are shared across the clade. Furthermore, the underlying genetic architecture of the transmission of asexuality, which can occur when rare males mate with closely related sexual females, is not well understood. We produced a chromosome-level assembly for the sexual Eurasian species A. sinica and characterized in detail the pair of sex chromosomes of this species. We combined this new assembly with short-read genomic data for the sexual species A. sp. Kazakhstan and several asexual lineages of A. parthenogenetica, allowing us to perform an in-depth characterization of sex-chromosome evolution across the genus. We identified a small differentiated region of the ZW pair that is shared by all sexual and asexual lineages, supporting the shared ancestry of the sex chromosomes. We also inferred that recombination suppression has spread to larger sections of the chromosome independently in the American and Eurasian lineages. Finally, we took advantage of a rare male, which we backcrossed to sexual females, to explore the genetic basis of asexuality. Our results suggest that parthenogenesis is likely partly controlled by a locus on the Z chromosome, highlighting the interplay between sex determination and asexuality.

[Pulmonary embolism as a presentation of nephrotic syndrome]

BACKGROUND

Nephrotic syndrome (NS) in adults is defined by proteinuria>3g/24h or 50mg/kg/d, hypoproteinemia<60g/24h and hypoalbuminemia<30g/L. The final diagnosis is guided by the histopathology evidence when a renal biopsy is possible. The consequences of NS are multiple: high blood pressure, undernutrition, infections and a hypercoagulable state.

OBSERVATION

We report the case of a patient presenting with thromboembolic disease, occurring in the absence of other thromboembolic risk factors, which revealed NS with spontaneously favorable evolution.

CONCLUSION

Thromboembolic disease in NS is frequent but underestimated and may remain underdiagnosed. Thorough investigation - including serum protein levels and testing for proteinuria - are essential in thromboembolism, as is excluding cancer or another cause. The treatment of thromboembolic disease in NS is based on anticoagulation for as long as the NS persists. There is no consensus about primary prophylaxis but an albumin level below 20g/L should be considered as a risk factor of thrombosis and prophylactic anticoagulation should be started.