Identification of the sex-determining factor in the liverwort Marchantia polymorpha reveals unique evolution of sex chromosomes in a haploid system

半数体生物の性染色体上の性決定遺伝子を解明 --コケがもつ現生生物最古の起源の性染色体--. 京都大学プレスリリース. 2021-11-08.Sex determination is a central process for sexual reproduction and is often regulated by a sex determinant encoded on a sex chromosome. Rules that govern the evolution of sex chromosomes via specialization and degeneration following the evolution of a sex determinant have been well studied in diploid organisms. However, distinct predictions apply to sex chromosomes in organisms where sex is determined in the haploid phase of the life cycle: both sex chromosomes, female U and male V, are expected to maintain their gene functions, even though both are non-recombining. This is in contrast to the X-Y (or Z-W) asymmetry and Y (W) chromosome degeneration in XY (ZW) systems of diploids. Here, we provide evidence that sex chromosomes diverged early during the evolution of haploid liverworts and identify the sex determinant on the Marchantia polymorpha U chromosome. This gene, Feminizer, encodes a member of the plant-specific BASIC PENTACYSTEINE transcription factor family. It triggers female differentiation via regulation of the autosomal sex-determining locus of FEMALE GAMETOPHYTE MYB and SUPPRESSOR OF FEMINIZATION. Phylogenetic analyses of Feminizer and other sex chromosome genes indicate dimorphic sex chromosomes had already been established 430 mya in the ancestral liverwort. Feminizer also plays a role in reproductive induction that is shared with its gametolog on the V chromosome, suggesting an ancestral function, distinct from sex determination, was retained by the gametologs. This implies ancestral functions can be preserved after the acquisition of a sex determination mechanism during the evolution of a dominant haploid sex chromosome system

〈Originals〉Relation between low take-off of the left atrial appendage and thromboembolic events in patients with atrial fibrillation : evaluation with multi-detector CT

[Abstract] The left atrial appendage (LA-Ap) is one of the major sources of cardiac thrombus formation responsible for thromboembolism inpatients with atrial fibrillation (AF). We hypothesized that the particular anatomical characteristics of the LA-Ap may facilitate thrombus formation. Methods : Seventy-four AF patients underwent transesophageal echocardiography (TEE) and multi-detector CT (MDCT) examinations. These patients were divided into two groups, with and without systemic embolism (Emb) [Emb (+) group, 10 patients, male/female =7/3 ; Emb (—) group, 64 patients, male/female = 51/13]. To evaluate the location of the LA-Ap in relation to the left atrium (LA), we determined four distinctive points on MDCT images using two carefully defined orthogonal sections : the superior summit of the mitral annulus (point-A), the anterior and posterior sites of the LA-Ap orifice (point-B and C), and the posterior LA (point-D). Next, we evaluated the relation of the geometrical intervals (A-B, B-C, C-D) to the prior thromboembolism. Results : Using multivariate analysis, a shorter A-B interval was recognized as an independent factor positively associated witha history of thromboembolism. Conclusion : The position of the LA-Ap orifice may affect the hemodynamic state of the LA-Ap, and anterior deviation of the LA-Ap orifice (low take-off of the LA-Ap) may be a risk factor for thrombus formation in LA-Ap and systemic embolism

Influence of ventricular morphology on aerobic exercise capacity in patients after the Fontan operation

AbstractOBJECTIVESThis study investigated the influences of ventricular morphology, hemodynamics and clinical findings on exercise capacity in patients after the Fontan operation.BACKGROUNDDeterminants of exercise capacity after the Fontan operation remain unclear.METHODSPeak oxygen uptake (PV̇o2) was determined in 105 patients by exercise test and compared to hemodynamics and clinical findings. Patients were divided into three groups based on ventricular morphology: those with a right ventricle (group RV), a biventricle (group BV) and a left ventricle (group LV).RESULTSTen patients with atrioventricular valve regurgitation (AVVR) or hypoxia exhibited a low PV̇o2. After excluding these patients, although PV̇o2did not correlate with hemodynamics, except ventricular ejection fraction (p < 0.02), it correlated with age at the Fontan operation and exercise test (p < 0.002). The PV̇o2was higher in group LV (63 ± 9%) than in groups RV (55 ± 9%) and BV (55 ± 12%) (p < 0.01), while an inverse correlation between PV̇o2and age at operation was demonstrated only in group RV (p < 0.05). Groups RV or BV and age at exercise test were associated with a lower PV̇o2, whereas group LV was an independent predictor of a higher PV̇o2(p < 0.01). During 4.2 years of follow-up, a decrease in peak heart rate was related to a decrease in PV̇o2(p < 0.05). The PV̇o2decreased in group RV (p < 0.01).CONCLUSIONSIn addition to AVVR, hypoxia, and heart rate response, ventricular morphology is related to exercise capacity. Early Fontan operation may be beneficial in terms of exercise capacity, especially in the group RV patients