The Cynosure of CtBP: Evolution of a Bilaterian Transcriptional Corepressor.

Evolution of sequence-specific transcription factors clearly drives lineage-specific innovations, but less is known about how changes in the central transcriptional machinery may contribute to evolutionary transformations. In particular, transcriptional regulators are rich in intrinsically disordered regions that appear to be magnets for evolutionary innovation. The C-terminal Binding Protein (CtBP) is a transcriptional corepressor derived from an ancestral lineage of alpha hydroxyacid dehydrogenases; it is found in mammals and invertebrates, and features a core NAD-binding domain as well as an unstructured C-terminus (CTD) of unknown function. CtBP can act on promoters and enhancers to repress transcription through chromatin-linked mechanisms. Our comparative phylogenetic study shows that CtBP is a bilaterian innovation whose CTD of about 100 residues is present in almost all orthologs. CtBP CTDs contain conserved blocks of residues and retain a predicted disordered property, despite having variations in the primary sequence. Interestingly, the structure of the C-terminus has undergone radical transformation independently in certain lineages including flatworms and nematodes. Also contributing to CTD diversity is the production of myriad alternative RNA splicing products, including the production of "short" tailless forms of CtBP in Drosophila. Additional diversity stems from multiple gene duplications in vertebrates, where up to five CtBP orthologs have been observed. Vertebrate lineages show fewer major modifications in the unstructured CTD, possibly because gene regulatory constraints of the vertebrate body plan place specific constraints on this domain. Our study highlights the rich regulatory potential of this previously unstudied domain of a central transcriptional regulator.

Quality of Life Predictors in Patients with Acute Lower Limb Ischemia Quality of Life in Acute Limb Ischemia.

OBJECTIVE: While existing literature has established factors associated with improved health-related quality of life (HRQOL) in patients with chronic limb-threatening ischemia, similar work has not been done in individuals with acute lower limb ischemia (ALLI). This study aims to identify the factors associated with HRQOL in patients presenting with ALLI. METHODS: Using a prospectively collected registry, all patients who received treatment for ALLI between May 2016 and July 2023 at a quaternary medical center were identified and invited to complete two HRQOL questionnaires: the VascuQoL-6 and the EQ-5D-5L. Simple linear regression followed by multivariate analysis using multiple linear regression were used to determine the patient variables independently associated with HRQOL. RESULTS: Of the 216 eligible patients treated for ALLI during the study period, 47 (20%) of patients with a mean age of 58 ± 10 years completed the HRQOL questionnaires. Questionnaires were completed at a median time of 16.5 months after the episode of ALLI. On multiple linear regression, higher age was associated with higher VascuQoL-6 (p=0.037) and EQ-5D-5L (p=0.041) scores, while hypertension and non-ambulatory status were significant predictors of lower VascuQoL-6 (p=0.006, p=0.013) and EQ-5D-5L (p=0.009, p=0.026) scores. Any ambulation had a significantly higher HRQOL compared to non-ambulatory status, but no significant HRQOL difference was observed between patients with any type of ambulation (unhindered ambulation, ambulation with pain, and ambulation using a prosthesis). CONCLUSION: This study demonstrates that the ability to ambulate after ALLI, and not amputation per se, is an important predictor of HRQOL. As such, early rehabilitation strategies should be a focus of post-ALLI care. Further exploration of factors that shape HRQOL after ALLI is needed.

Diversification of Retinoblastoma Protein Function Associated with Cis and Trans Adaptations.

Retinoblastoma proteins are eukaryotic transcriptional corepressors that play central roles in cell cycle control, among other functions. Although most metazoan genomes encode a single retinoblastoma protein, gene duplications have occurred at least twice: in the vertebrate lineage, leading to Rb, p107, and p130, and in Drosophila, an ancestral Rbf1 gene and a derived Rbf2 gene. Structurally, Rbf1 resembles p107 and p130, and mutation of the gene is lethal. Rbf2 is more divergent and mutation does not lead to lethality. However, the retention of Rbf2 >60 My in Drosophila points to essential functions, which prior cell-based assays have been unable to elucidate. Here, using genomic approaches, we provide new insights on the function of Rbf2. Strikingly, we show that Rbf2 regulates a set of cell growth-related genes and can antagonize Rbf1 on specific genes. These unique properties have important implications for the fly; Rbf2 mutants show reduced egg laying, and lifespan is reduced in females and males. Structural alterations in conserved regions of Rbf2 gene suggest that it was sub- or neofunctionalized to develop specific regulatory specificity and activity. We define cis-regulatory features of Rbf2 target genes that allow preferential repression by this protein, indicating that it is not a weaker version of Rbf1 as previously thought. The specialization of retinoblastoma function in Drosophila may reflect a parallel evolution found in vertebrates, and raises the possibility that cell growth control is equally important to cell cycle function for this conserved family of transcriptional corepressors.

Benign Metastasizing Leiomyoma in a Patient With No Known History of Uterine Leiomyomas.

Benign metastasizing leiomyoma (BML) is a rare medical condition characterized by metastasis of fibroid tissue from uterine leiomyomas to other areas of the body, most commonly the lungs. While BML is mostly prevalent in women with a prior history of uterine leiomyomas who underwent surgical intervention, this case report explores the case of a 50-year-old female who was diagnosed with pulmonary benign metastasizing leiomyoma (PBML) with no prior history of confirmed leiomyomas. After initially presenting with worsening cough and congestion, chest radiograph and computed tomography revealed multiple bilateral pulmonary nodules, initially raising concerns for malignancy. Further, a workup with bronchoscopy with fine needle aspiration and pulmonary lesion biopsy revealed the presence of smooth muscle tissue suggestive of PBML. Subsequent uterine ultrasonography revealed a 3-cm intramural uterine fibroid, supporting the diagnosis. This case highlights the diagnostic challenge posed by PBML due to its asymptomatic manifestation and radiological similarity with other serious conditions such as malignancy and sarcoidosis. The case further highlights the importance of recognizing typical radiological features of PBML and the necessity of histological examination for accurate diagnosis. Finally, the critical role of a multidisciplinary approach in managing such rare conditions and the need for individualized treatment are also explored.

Selective repression of the Drosophila cyclin B promoter by retinoblastoma and E2F proteins.

The Cyclin B1 gene encodes a G2/M cyclin that is deregulated in various human cancers, however, the transcriptional regulation of this gene is incompletely understood. The E2F and retinoblastoma family of proteins are involved in this gene's regulation, but there is disagreement on which of the E2F and retinoblastoma proteins interact with the promoter to regulate this gene. Here, we dissect the promoter region of the Drosophila CycB gene, and study the role of Rbf and E2F factors in its regulation. This gene exhibits remarkable features that distinguish it from G1/S regulated promoters, such as PCNA. The promoter is comprised of modular elements with dedicated repressor and activator functions, including a segment spanning the first intron that interferes with a 5' activator element. A highly active minimal promoter (-464, +100) is repressed by the Rbf1 retinoblastoma protein, but much more potently repressed by the Rbf2 protein, which has been linked in other studies to control of cell growth genes. Unlike many other cell-cycle genes, which are activated by E2F1 and repressed by E2F2, CycB is potently activated by E2F2, and repressed by E2F1. Although the bulk of Rbf binding is associated with a region 5' of the core promoter, E2F and retinoblastoma proteins functionally interact with the basal promoter region, in part through a conserved E2F site at -80 bp. The specific regulatory requirements of this late cell cycle promoter appear to be linked to the unique activities of E2F and retinoblastoma family members acting on a complex cis-regulatory circuit.