Transitions in development - an interview with Bhavana Muralidharan.

Bhavana Muralidharan is an Assistant Professor at the Institute for Stem Cell Science and Regenerative Medicine (inStem), where her research focuses on chromatin-mediated regulation of neurodevelopment and neuropsychiatric disorders, and the development of cerebral organoids for modelling these disorders in vitro. We caught up with Bhavana over Zoom to discuss her research, the recent EMBO organoid meeting hosted at inStem and her creative performances outside of the lab.

Transitions in Development - an interview with Jingli Cao.

Jingli Cao is an Assistant Professor of Cell and Developmental Biology at Weill Cornell Medical College, USA, where he started his own lab in 2018. Jingli's research focuses on uncovering the cellular and molecular mechanisms that underpin the regenerative capacity of the zebrafish heart. We spoke with Jingli over Zoom to find out more about his career path, his experience of becoming a group leader and his love for astronomy.

An interview with Tyler Huycke.

Tyler Huycke is a postdoctoral researcher in Zev Gartner's and Ophir Klein's labs at the University of California San Francisco (UCSF), where he studies the relationship between mechanics and tissue patterning during gut morphogenesis. Tyler served as an editor for the Journal of Emerging Investigators and as a student co-leader of the developmental and regenerative biology graduate programme at Harvard University. He was awarded the Young Investigator's Award at the 2022 Santa Cruz Developmental Biology (SCDB) meeting, which celebrates outstanding early career researchers. I caught up with Tyler at the SCDB meeting to discuss the award, his research and his career.

The scaffolding protein flot2 promotes cytoneme-based transport of wnt3 in gastric cancer.

The Wnt/ß-catenin signalling pathway regulates multiple cellular processes during development and many diseases, including cell proliferation, migration, and differentiation. Despite their hydrophobic nature, Wnt proteins exert their function over long distances to induce paracrine signalling. Recent studies have identified several factors involved in Wnt secretion; however, our understanding of how Wnt ligands are transported between cells to interact with their cognate receptors is still debated. Here, we demonstrate that gastric cancer cells utilise cytonemes to transport Wnt3 intercellularly to promote proliferation and cell survival. Furthermore, we identify the membrane-bound scaffolding protein Flotillin-2 (Flot2), frequently overexpressed in gastric cancer, as a modulator of these cytonemes. Together with the Wnt co-receptor and cytoneme initiator Ror2, Flot2 determines the number and length of Wnt3 cytonemes in gastric cancer. Finally, we show that Flotillins are also necessary for Wnt8a cytonemes during zebrafish embryogenesis, suggesting a conserved mechanism for Flotillin-mediated Wnt transport on cytonemes in development and disease.

Tollip coordinates Parkin-dependent trafficking of mitochondrial-derived vesicles.

Multiple mitochondrial quality control pathways exist to maintain the health of mitochondria and ensure cell homeostasis. Here, we investigate the role of the endosomal adaptor Tollip during the mitochondrial stress response and identify its interaction and colocalisation with the Parkinson's disease-associated E3 ubiquitin ligase Parkin. The interaction between Tollip and Parkin is dependent on the ubiquitin-binding CUE domain of Tollip, but independent of Tom1 and mitophagy. Interestingly, this interaction is independent of Parkin mitochondrial recruitment and ligase activity but requires an intact ubiquitin-like (UBL) domain. Importantly, Tollip regulates Parkin-dependent endosomal trafficking of a discrete subset of mitochondrial-derived vesicles (MDVs) to facilitate delivery to lysosomes. Retromer function and an interaction with Tom1 allow Tollip to facilitate late endosome/lysosome trafficking in response to mitochondrial stress. We find that upregulation of TOM20-positive MDVs upon mitochondrial stress requires Tollip interaction with ubiquitin, endosomal membranes and Tom1 to ensure their trafficking to the lysosomes. Thus, we conclude that Tollip, via an association with Parkin, is an essential coordinator to sort damaged mitochondrial-derived cargo to the lysosomes.

Mechanisms of intercellular Wnt transport.

Wnt proteins are secreted glycoproteins that regulate multiple processes crucial to the development and tissue homeostasis of multicellular organisms, including tissue patterning, proliferation, cell fate specification, cell polarity and migration. To elicit these effects, Wnts act as autocrine as well as paracrine signalling molecules between Wnt-producing and Wnt-receiving cells. More than 40 years after the discovery of the Wg/Wnt pathway, it is still unclear how they are transported to fulfil their paracrine signalling functions. Several mechanisms have been proposed to mediate intercellular Wnt transport, including Wnt-binding proteins, lipoproteins, exosomes and cytonemes. In this Review, we describe the evidence for each proposed mechanism, and discuss how they may contribute to Wnt dispersal in tissue-specific and context-dependent manners, to regulate embryonic development precisely and maintain the internal steady state within a defined tissue.

Does delta-sarcoglycan-associated autosomal-dominant cardiomyopathy exist?

In this study we clinically and genetically characterize a consanguineous family with a homozygous novel missense mutation in the delta-sarcoglycan gene and a second delta-sarcoglycan mutation that has previously been reported to cause severe autosomal-dominant dilated cardiomyopathy. We identified a novel missense mutation in exon 6 (p.A131P) of the delta-sarcoglycan gene, which in a homozygous state leads to the clinical picture of a limb girdle muscular dystrophy. In four heterozygous carriers for the mutation, aged 3-64 years, a second sequence variant in exon 6 (p.S151A) of the delta-sarcoglycan gene was detected on the other allele. This second missense change had previously been reported to be responsible for fatal autosomal-dominant dilated cardiomyopathy at young age. Comprehensive clinical and cardiac investigation in all of the compound heterozygous family members revealed no signs of cardiomyopathy or limb girdle muscular dystrophy. Our findings demonstrate that, even in the presence of a second disease-causing mutation, the p.S151A mutation in the delta-sarcoglycan gene does not result in cardiomyopathy. This finding questions the pathological relevance of this sequence variant for causing familial autosomal-dominant dilated cardiomyopathy and thereby the role of the delta-sarcoglycan gene in general as a disease-causing gene for autosomal-dominant dilated cardiomyopathy.

Quantitative assessment of mixed chimerism in allogeneic stem cell transplant patients: a comparison of molecular genetic and cytogenetic approaches.

After allogeneic stem cell transplantation, dual donor and recipient populations may be present. Donor/recipient ratio changes over time may predict clinical outcome: accurate measurement of these changes are needed. Chimerism may be measured by XY-fluorescence in situ hybridization for donor/recipient sex mismatch, or polymerase chain reaction amplification of short tandem repeat loci with donor/recipient sex match. Patients were monitored by each method. Additionally, mononuclear cells from 2 sex-mismatched individuals were mixed and analyzed using both methods. Each gave concordant estimates of patient chimerism and discriminated cell population ratios in mixed blood. We conclude that cytogenetic and molecular methods give accurate donor chimerism estimates.