The Arabidopsis katamari2 Mutant Exhibits a Hypersensitive Seedling Arrest Response at the Phase Transition from Heterotrophic to Autotrophic Growth.

Young seedlings use nutrients stored in the seeds to grow and acquire photosynthetic potential. This process, called seedling establishment, involves a developmental phase transition from heterotrophic to autotrophic growth. Some membrane-trafficking mutants of Arabidopsis (Arabidopsis thaliana), such as the katamari2 (kam2) mutant, exhibit growth arrest during seedling development, with a portion of individuals failing to develop true leaves on sucrose-free solid medium. However, the reason for this seedling arrest is unclear. In this study, we show that seedling arrest is a temporal growth arrest response that occurs not only in kam2 but also in wild-type (WT) Arabidopsis; however, the threshold for this response is lower in kam2 than in the WT. A subset of the arrested kam2 seedlings resumed growth after transfer to fresh sucrose-free medium. Growth arrest in kam2 on sucrose-free medium was restored by increasing the gel concentration of the medium or covering the surface of the medium with a perforated plastic sheet. WT Arabidopsis seedlings were also arrested when the gel concentration of sucrose-free medium was reduced. RNA sequencing revealed that transcriptomic changes associated with the rate of seedling establishment were observed as early as 4 d after sowing. Our results suggest that the growth arrest of both kam2 and WT seedlings is an adaptive stress response and is not simply caused by the lack of a carbon source in the medium. This study provides a new perspective on an environmental stress response under unfavorable conditions during the phase transition from heterotrophic to autotrophic growth in Arabidopsis.

Comprehensive Risk Assessment in Patients With Pulmonary Arterial Hypertension Referred for Lung Transplantation.

BACKGROUND: Whether comprehensive risk assessment predicts post-referral outcome in patients with pulmonary arterial hypertension (PAH) referred for lung transplantation (LT) in Japan is unknown.Methods and Results: We retrospectively analyzed 52 PAH patients referred for LT. Risk status at referral was assessed using 3- and 4-strata models from the 2022 European Society of Cardiology and European Respiratory Society guidelines. The 3-strata model intermediate-risk group was further divided into 2 groups based on the median proportion of low-risk variables (modified risk assessment [MRA]). The primary outcome was post-referral mortality. During follow-up, 9 patients died and 13 patients underwent LT. There was no survival difference among 3-strata model groups. The 4-strata model classified 33, 16, and 3 patients as low intermediate, high intermediate, and high risk, respectively. The 4-strata model identified high-risk patients with a 1-year survival rate of 33%, but did not discriminate survival between the intermediate-risk groups. The MRA classified 15, 28, 8, and 1 patients as low, low intermediate, high intermediate, and high risk, respectively. High intermediate- or high-risk patients had worse survival (P<0.001), with 1- and 3-year survival rates of 64% and 34%, respectively. MRA high intermediate- or high-risk classification was associated with mortality (hazard ratio 12.780; 95% confidence interval 2.583-63.221; P=0.002). CONCLUSIONS: Patients classified as high intermediate or high risk by the MRA after treatment should be referred for LT.

Differential effects of balloon pulmonary angioplasty on chronic thromboembolic pulmonary disease.

BACKGROUND: Decreased diffusing capacity of the lungs for carbon monoxide (DLco) is associated with microvascular damage in chronic thromboembolic pulmonary hypertension (CTEPH). Balloon pulmonary angioplasty (BPA) is an effective treatment for CTEPH, but the efficacy of BPA in patients with CTEPH with low DLco remains unclear because BPA does not directly address microvascular damage. This study investigates the influence of microvasculopathy on BPA in CTEPH according to DLco. METHODS: We retrospectively analysed data from patients with inoperable CTEPH who underwent BPA at the University of Tokyo Hospital from July 2011 to August 2023. The patients were classified into two groups based on their preprocedural DLco (normal DLco (ND) and low DLco (LD) groups), with a DLco cut-off value of 80%. We compared the patient characteristics and effectiveness of BPA between the groups. RESULTS: Among the 75 patients, 36 were in the LD group. The LD group had a shorter 6-minute walking distance (324±91 vs 427±114 m) than the ND group but the mean pulmonary artery pressure (mPAP) was similar (38.9±7.3 vs 41.1±9.2 mm Hg) before BPA. BPA improved the haemodynamic status and exercise tolerance in both groups. The LD group exhibited a higher mPAP (25.1±7.4 vs 21.5±5.6 mm Hg) and required more sessions of BPA (median 6 vs 4). Based on the analysis of covariance adjusted for baseline values, low DLco significantly correlated with mPAP (sß=-0.304, 95% CI -7.015 to -1.132, p=0.007) and pulmonary vascular resistance (sß=-0.324, 95% CI -141.0 to -29.81, p=0.003). CONCLUSIONS: BPA was associated with an improvement in the haemodynamic status and exercise tolerance in patients with CTEPH even with low DLco. However, low DLco may attenuate the effect of BPA on mPAP and pulmonary vascular resistance and require more treatment sessions.

Management of an elderly patient with nonsyndromic TGFBR1-related aortopathy: A case report.

Key Clinical Message: Genetic variants associated with hereditary TAAD may contribute to nonsyndromic TAAD. We present the case of a 72-year-old man with nonsyndromic TAAD undergoing prophylactic surgery after a gene panel test revealed a pathogenic variant in TGFBR1, but the indication for genetic testing in such elderly-onset cases still warrants further discussion. Abstract: Hereditary thoracic aortic aneurysm and dissection (TAAD) is a serious clinical condition resulting in a fatal outcome. Recently, variants in causative genes for syndromic hereditary TAAD, such as Marfan syndrome and Loeys-Dietz syndrome (LDS), have been reported to predispose to the development of nonsyndromic TAAD; however, genetic testing for patients with elderly-onset nonsyndromic TAAD warrants further discussion. We present a 72-year-old nonsyndromic Japanese man with moderate-sized aortic annulus ectasia (AAE) with moderate aortic regurgitation and ascending to distal arch aortic dilatation (maximum diameter: 46 mm). He had been treated for hypertension and dyslipidemia for 7 years, and his eldest son had AAE at 33 years old and type A aortic dissection at 43 years old. Surgical repair was considered a treatment option because the patient potentially had a nonsyndromic hereditary aortic disease, and genetic panel testing for TAAD identified a pathogenic missense variant in TGFBR1 (c.934G > A, p.[Gly312Ser]), previously reported in patients with LDS type 1. He was diagnosed with nonsyndromic TGFBR1-related aortopathy and underwent prophylactic surgery using a modified Bentall operation and total arch replacement with open stent graft implantation. Genetic testing was useful in guiding the treatment strategy, but further analysis is warranted to establish the clinical value in the treatment plan for patients with elderly-onset nonsyndromic TAAD.