Extensive non-redundancy in a recently duplicated developmental gene family.

BACKGROUND: It has been proposed that recently duplicated genes are more likely to be redundant with one another compared to ancient paralogues. The evolutionary logic underpinning this idea is simple, as the assumption is that recently derived paralogous genes are more similar in sequence compared to members of ancient gene families. We set out to test this idea by using molecular phylogenetics and exploiting the genetic tractability of the model nematode, Caenorhabditis elegans, in studying the nematode-specific family of Hedgehog-related genes, the Warthogs. Hedgehog is one of a handful of signal transduction pathways that underpins the development of bilaterian animals. While having lost a bona fide Hedgehog gene, most nematodes have evolved an expanded repertoire of Hedgehog-related genes, ten of which reside within the Warthog family. RESULTS: We have characterised their evolutionary origin and their roles in C. elegans and found that these genes have adopted new functions in aspects of post-embryonic development, including left-right asymmetry and cell fate determination, akin to the functions of their vertebrate counterparts. Analysis of various double and triple mutants of the Warthog family reveals that more recently derived paralogues are not redundant with one another, while a pair of divergent Warthogs do display redundancy with respect to their function in cuticle biosynthesis. CONCLUSIONS: We have shown that newer members of taxon-restricted gene families are not always functionally redundant despite their recent inception, whereas much older paralogues can be, which is considered paradoxical according to the current framework in gene evolution.

How can we help? Medical students' views on their role in the COVID-19 pandemic.

BACKGROUND: The ongoing COVID-19 pandemic has resulted in a sharp rise in demand for healthcare workers worldwide. This has been coupled with reduced numbers of available medical professionals due to confirmed or suspected infections with SARS-CoV-2. To counteract these shortages, governments of several countries have considered the enrolment of medical students into the workforce in order to help to tackle the ongoing crisis. METHODS: Questionnaire-based study assessing the perceived role of medical students in assisting in the COVID-19 pandemic. The primary aim was to determine factors contributing to the willingness of medical students to actively assist in the pandemic. The secondary aim was to evaluate their perspectives regarding the associated changes in medical education. RESULTS: Out of 760 responses, 71.18% of medical students were willing to assist the medical workforce during the pandemic. Clinical year students were more likely to help in a medical capacity than pre-clinical students (OR = 0.384, 95%CI [0.167, 0.883, P < 0.05)]. Respondents concerned about their own well-being were less likely to engage in clinical work (OR = 0.680, 95%CI [0.491, 0.941], P < 0.020). Students who agreed that online lectures will negatively impact their education were inclined to think that the academic year should be extended (95%CI [0.065, 0.271], P = 0.001). CONCLUSIONS: Most students are willing to help in both a medical and non-medical capacity. Their primary concerns when working in a medical setting are the risk of infecting their relatives and patients, lack of protective equipment and necessary knowledge as well as legal uncertainty whilst working without a medical qualification.

Neuromuscular reinnervation efficacy using a YFP model.

INTRODUCTION: The gold standard reconstruction for facial reanimation is the functional muscle transfer. The reinnervation of a muscle is never complete, and clinical results are variable with 20% not achieving a satisfactory outcome. We hypothesise that this may be due to a mismatch between the characteristics of the donor nerve and transferred muscle. METHOD: 81 YFP-16 and 14 YFP-H mice were studied in three intervention groups over three time periods. Two parameters were investigated: the number and surface area of reinnervated neuromuscular junctions and regenerating axons. An assessment was made of motor unit proportions. RESULTS: All cases of nerve repair and nerve graft, the neuromuscular junctions (NMJ) were completely reinnervated by regenerating axons. The number and calibre of the regenerating axons were significantly different from controls for both intervention groups. The motor units were smaller in both intervention groups. DISCUSSION: Reinnervation occurs after nerve repair or graft; however, the arbour was reinnervated by large numbers of much smaller axons. These axons showed some evidence of remodelling in the repair group, but not in the graft group. Neither group achieved the parameters of the control group. There were persistent qualitative changes to the morphology of both axons and junctions. Imaging documented both synkinesis and alterations that resemble those seen in ageing. CONCLUSION: Overall, the efficacy of reinnervation is very high with all NMJ reoccupied by regenerating axons. The way small axons are remodelled is different in the nerve repairs compared with the nerve grafts.

RUNX in Invertebrates.

Runx genes have been identified in all metazoans and considerable conservation of function observed across a wide range of phyla. Thus, insight gained from studying simple model organisms is invaluable in understanding RUNX biology in higher animals. Consequently, this chapter will focus on the Runx genes in the diploblasts, which includes sea anemones and sponges, as well as the lower triploblasts, including the sea urchin, nematode, planaria and insect. Due to the high degree of functional redundancy amongst vertebrate Runx genes, simpler model organisms with a solo Runx gene, like C. elegans, are invaluable systems in which to probe the molecular basis of RUNX function within a whole organism. Additionally, comparative analyses of Runx sequence and function allows for the development of novel evolutionary insights. Strikingly, recent data has emerged that reveals the presence of a Runx gene in a protist, demonstrating even more widespread occurrence of Runx genes than was previously thought. This review will summarize recent progress in using invertebrate organisms to investigate RUNX function during development and regeneration, highlighting emerging unifying themes.

The outcomes of digital tip amputation replacement as a composite graft in a paediatric population.

UNLABELLED: Limited studies exist on the outcome of replacing an amputated fingertip as a composite graft. We report the outcomes and predictors for composite graft survival along with the long-term morbidity. A retrospective review of all patients <16 years who underwent composite graft replacement of an amputated fingertip was performed. Long-term morbidity was evaluated through a standardized parental questionnaire. A total of 120 patients were identified, of whom 97 were eligible for inclusion. Parental questionnaires were completed for 42 (43%) patients. There was a 10% complete and 34% partial graft survival rate. Patients aged ⩽4 were significantly more likely to have complete graft take than those >4. Of the patients, 17% developed post-operative complications; 48% of patients reported a hook-nail deformity and 17% reported cold intolerance. Only 5% of patients reported any functional difficulties long term. The rate of complete composite graft survival in a paediatric population is low, although the long-term function of these patients is good. LEVEL OF EVIDENCE: 3.

The influence of essential oils on the process of wound healing: a review of the current evidence.

This paper reports on a literature review of evidence on the influence of essential oils on wound healing and their potential application in clinical practice. It focuses mainly on tea tree, lavender, chamomile, thyme and ocimum oils.

The caenorhabditis elegans fate-determining gene mab-9 encodes a T-box protein required to pattern the posterior hindgut.

Caenorhabditis elegans mab-9 mutants are defective in hindgut and male tail development because of cell fate transformations in two posterior blast cells, B and F. We have cloned mab-9 and show that it encodes a member of the T-box family of transcriptional regulators. MAB-9 localizes to the nucleus of B and F and their descendents during development, suggesting that it acts cell autonomously in the posterior hindgut to direct cell fate. T-box genes related to brachyury have also been implicated in hindgut patterning, and our results support models for an evolutionarily ancient role for these genes in hindgut formation.

Analysis of the cps1 gene provides evidence for a septation checkpoint in Schizosaccharomyces pombe.

The fission yeast gene cps1, which encodes the catalytic subunit of beta-glucan synthase, was isolated in a screen for mutants that show an increase in ploidy at the restrictive temperature. cps1 mutants display defects in both polarity and septation at the permissive temperature, and become swollen and multinucleate at the restrictive temperature. Analysis of the interaction of cps1 with other mutations suggests the existence of a septation checkpoint, which requires the activity of the protein kinase weel for function.

Stu-7/air-2 is a C. elegans aurora homologue essential for chromosome segregation during embryonic and post-embryonic development.

We have isolated a new sterile uncoordinated C. elegans mutant, stu-7, which is defective in post-embryonic cell divisions in a regionally-specific fashion. The anterior of the worm is relatively unaffected whereas the mid-body and/or posterior are markedly thin, often resulting in worms having a central 'waist'. We have cloned stu-7 and found that it encodes a member of the recently expanding aurora sub-family of serine/threonine kinases. Elimination of maternal as well as zygotic stu-7 expression reveals that stu-7 is essential for mitosis from the first embryonic cell cycle onwards and is required for chromosome segregation though not for centrosome separation or for setting up a bipolar spindle. Multicopy expression of stu-7 also causes mitotic defects, suggesting that the level of this protein must be tightly controlled in order to maintain genetic stability during development.

The Spg1p GTPase is an essential, dosage-dependent inducer of septum formation in Schizosaccharomyces pombe.

The spg1 gene (septum-promoting GTPase) was cloned as a multicopy suppressor of a dominant-negative mutant of the Cdc7p kinase. It encodes a small GTPase of the Ras superfamily. spg1 is an essential gene. Null or heat-sensitive alleles do not make a division septum, but growth, S-phase, and mitosis continue in the absence of cell division, producing elongated, multinucleate cells. Increased expression of Spg1p induces septum formation in G2, S-phase, and pre-Start G1-arrested cells. This requires the activity of Cdc7p kinase, but not p34(cdc2). Increased expression of Cdc7p bypasses the requirement for Spg1p. Spg1p and Cdc7p can be coimmunoprecipitated from cell extracts, and interact in the two-hybrid system. These data indicate that Spg1p is a key element in controlling the onset of septum formation in Schizosaccharomyces pombe, and that it acts through the Cdc7p kinase.

A novel S phase inhibitor in fission yeast.

We have cloned a novel fission yeast gene, spd1, which causes G1 arrest when overexpressed. Deleting the gene results in cells being accelerated through G1 into S phase in certain circumstances when the G1-->S phase control is compromised. We have found that the encoded 14 kDa protein is cell cycle regulated, declining in level during S phase, and that p14spd1 physically associates with p34cdc2 in vivo when overexpressed, suggesting that p14spd1 may regulate S phase progression via an interaction with p34cdc2. We conclude that p14spd1 is a negative regulator of S phase, and that it may be part of the control ensuring an orderly onset of S phase or part of a G1-->S phase checkpoint control.

Isolation and characterization of fission yeast mutants defective in the assembly and placement of the contractile actin ring.

Fission yeast cells divide by medial cleavage using an actin-based contractile ring. We have conducted a genetic screen for temperature-sensitive mutants defective in the assembly and placement of this actin ring. Six genes necessary for actin ring formation and one gene necessary for placement of the actin ring have now been identified. The genes can be further organized into different phenotypic groups, suggesting that the gene products may have different functions in actin ring formation. Mutants of cdc3 and cdc8, which encode profilin and tropomyosin respectively, display disorganized actin patches in all cells. cdc12 and cdc15 mutants display disorganized actin patches during mitosis, but normal interphase actin patterns. cdc4 and rng2 mutants display disorganized actin cables during mitosis, but normal interphase actin patterns. In mid1 mutants, the actin ring and septum are positioned at random locations and angles on the cell surface, although the nucleus is positioned normally, indicating that the mid1 gene product is required to couple the division site to the position of the nucleus. mid1 mutant cells may reveal a new cell cycle checkpoint in telophase that coordinates cell division and the proper distribution of nuclei. The actin ring forms medially in a beta-tubulin mutant, showing that actin ring formation and placement are not dependent on the mitotic spindle.

G1 regulation and checkpoints operating around START in fission yeast.

Three major aspects of G1 regulation acting at START in fission yeast are discussed in this review. Firstly, progression towards S phase in the mitotic cycle. This is controlled by the activation of transcription complexes at START which cause cell cycle-dependent activation of genes required for DNA synthesis. The second aspect is the regulation of developmental fate occurring during G1. Passage through START appears to inhibit sexual differentiation because the meiotic and mitotic pathways are mutually exclusive. This is brought about because the meiotic pathway is inhibited by the same gene functions that are required for S phase onset. Thirdly, distinct checkpoint, or dependency, controls operate both pre- and post-START in the mitotic cycle to inhibit mitosis in the absence of replicated DNA, and also to limit rounds of DNA replication to one per cell cycle.