Comparing the effects of three neonicotinoids on embryogenesis of the South African clawed frog Xenopus laevis

Neonicotinoids (NEOs) are widely used insecticides that are ubiquitous in agricultural use. Since NEOs are found in natural waters as well as in tap water and human urine in regions where NEOs are widely used, NEOs pose a potential hazard to non-target organisms such as animals and humans. Some of the commonly detected NEOs are imidacloprid (IMD), thiamethoxam (TMX), and its metabolite clothianidin (CLO). Although previously published scientific information, including an assessment of the environmental risks, particularly for bees, had resulted in a ban on the outdoor use of these three NEOs in the EU - their use is now only permitted in closed greenhouses - these NEOs continue to be used in agriculture in many other parts of the world. Therefore, a detailed study and comparison of the effects of NEOs on the embryonic development of non-target organisms is needed to further define the risk profiles. Embryos of the South African clawed frog Xenopus laevis, a well-established aquatic model, were exposed to different concentrations of IMD, TMX, or CLO (0.1-100 mg/L) to study and compare the possible effects of a single contaminant in natural water bodies on early embryogenesis. The results included a reduced body length, a smaller orbital space, impaired cranial cartilage and nerves, and an altered heart structure and function. At the molecular level, NEO exposure partially resulted in an altered expression of tissue-specific factors, which are involved in eye, cranial placode, and heart development. Our results suggest that the NEOs studied negatively affect the embryonic development of the non-target organism X. laevis. Since pesticides, especially NEOs, pollute the environment worldwide, it is suggested that they are strictly controlled and monitored in the areas where they are used. In addition, the question arises as to whether pesticide metabolites also pose a risk to the environment and need to be investigated further so that they can be taken into account when registering ingredients.

Prdm15 acts upstream of Wnt4 signaling in anterior neural development of Xenopus laevis

Mutations in PRDM15 lead to a syndromic form of holoprosencephaly (HPE) known as the Galloway-Mowat syndrome (GAMOS). While a connection between PRDM15, a zinc finger transcription factor, and WNT/PCP signaling has been established, there is a critical need to delve deeper into their contributions to early development and GAMOS pathogenesis. We used the South African clawed frog Xenopus laevis as the vertebrate model organism and observed that prdm15 was enriched in the tissues and organs affected in GAMOS. Furthermore, we generated a morpholino oligonucleotide-mediated prdm15 knockdown model showing that the depletion of Prdm15 leads to abnormal eye, head, and brain development, effectively recapitulating the anterior neural features in GAMOS. An analysis of the underlying molecular basis revealed a reduced expression of key genes associated with eye, head, and brain development. Notably, this reduction could be rescued by the introduction of wnt4 RNA, particularly during the induction of the respective tissues. Mechanistically, our data demonstrate that Prdm15 acts upstream of both canonical and non-canonical Wnt4 signaling during anterior neural development. Our findings describe severe ocular and anterior neural abnormalities upon Prdm15 depletion and elucidate the role of Prdm15 in canonical and non-canonical Wnt4 signaling.

The impact of the insecticide acetamiprid on the embryogenesis of the aquatic model organism Xenopus laevis

Acetamiprid (ACT) is used extensively in agriculture worldwide, although data on ACT concentrations in natural water bodies and its impact on aquatic organisms are limited. To study whether ACT influences the embryogenesis of the South African clawed frog Xenopus laevis, embryos were incubated in ACT solutions from 0.01 to 100 mg/L. The low concentrations were chosen on the basis of concentrations already found in nature. ACT treatment leads to shorter embryo lengths, intestine malformation and reduced eye areas. It also affects the cranial cartilage and cardiac development as well as the embryo's mobility. The expression of tissue-specific marker genes is affected as well. Thus, our study suggests that pesticides may lead to an increased mortality of non-target organisms and emphasizes the importance of regular testing for ACT concentrations in nature. Our study provides an overview of ACT effects and can therefore be used as a basis for an ACT risk assessment.

Medical students in their first consultation: A comparison between a simulated face-to-face and telehealth consultation to train medical consultation skills

Objective

A simulated conversation between a physician and a family member, i.e., a medical conversation, was changed from a conventional face-to-face conversation (SS 2019) to a telehealth conversation (SS 2020) due to the COVID-19 pandemic. The medical education conversation is part of the biochemistry seminar "From Genes to Proteins" which second semester human medicine students take. The objective of this study was to analyze to what extent the switch from face-to-face to telehealth conversations affected student satisfaction and motivation.

Methodology

In the seminar, students study biochemical as well as competency-oriented content, such as how to talk to family members. In the summer semester of 2019, students were trained how to talk to their patients' family members in a traditional conversation setting with the help of lay actors in a classroom format. In the summer semester of 2020, this conversation took place under comparable conditions, but in the form of an online telehealth conversation instead. Student satisfaction and motivation were surveyed by means of an evaluation questionnaire following the seminar in both semesters.

Results

Both conversation formats achieved a high level of satisfaction from students (school grade A-B). For some evaluation items, such as "realistic conversation simulation", the face-to-face conversation was perceived as more satisfying (Md=5.0, IQR=1.0) than the telehealth conversation (Md=5.0, IQR=2.0). In addition, the face-to-face conversation resulted in higher subjective motivation from students (Md=5.0, IQR=1.0) than that of the telehealth conversation (Md=4.0, IQR=2.0).

Conclusion

The high student satisfaction and acceptance of both didactic concepts leads to the conclusion that the simulated telehealth conversation is an adequate substitute for the simulation of a traditional face-to-face conversation with regard to the parameters that were studied.

Glyphosate without Co-formulants affects embryonic development of the south african clawed frog Xenopus laevis

BACKGROUND

Glyphosate (GLY) is the most widely used herbicide in the world. Due to its mode of action as an inhibitor of the 5-enolpyruvylshikimate-3-phosphate synthase, an important step in the shikimate pathway, specifically in plants, GLY is considered to be of low toxicity to non-target organisms. However, various studies have shown the negative effects of GLY on the mortality and development of different non-target organisms, including insects, rodents, fish and amphibians. To better understand the various effects of GLY in more detail, we studied the effects of GLY without co-formulants during the embryogenesis of the aquatic model organism Xenopus laevis.

RESULTS

A treatment with GLY affected various morphological endpoints in X. laevis tadpoles (body length, head width and area, eye area). Additionally, GLY interfered with the mobility as well as the neural and cardiac development of the embryos at stage 44/45. We were able to detect detailed structural changes in the cranial nerves and the heart and gained insights into the negative effects of GLY on cardiomyocyte differentiation.

CONCLUSION

The application of GLY without co-formulants resulted in negative effects on several endpoints in the early embryonic development of X. laevis at concentrations that are environmentally relevant and concentrations that reflect the worst-case scenarios. This indicates that GLY could have a strong negative impact on the survival and lives of amphibians in natural waters. As a result, future GLY approvals should consider its impact on the environment.

[Environmental knowledge and environmental awareness among Generation Z students: An online survey at the University of Ulm]

BACKGROUND

The issues of climate change, environmental pollution and species extinction play an increasingly central role in the public debate. At the same time, however, there is a significant gap between environmental knowledge and sustainable action (so-called value-action gap). The education system, especially at the university level, is an important institution for imparting well-founded knowledge on this topic and, as a consequence, for deriving targeted options for action. The present study surveyed the current environmental knowledge and environmental awareness, including the everyday behavior of Generation Z students of medical study programs in comparison to science-oriented study programs.

METHODS

In October/November 2021, an anonymous and voluntary online survey was conducted at the University of Ulm to evaluate the environmental knowledge and awareness of students in all semesters of the study programs Human Medicine, Dentistry, Molecular Medicine, Biology and Teaching. A total of 317 students fully completed the questionnaire.

RESULTS

The results confirm the current state of studies on the environmental awareness of the German population. The value-action gap is also detectable among students. Students perceive the urgency of environmental protection measures and action on climate change and also link these with emotional feelings, but in terms of behavior personal interests (still) tend to largely take precedence over environmental protection. In addition, according to our findings, the image of stereotypes and prejudices of the various courses of study is also partially confirmed in the surveyed environmental awareness.

CONCLUSION

The significant differences in environmental awareness between the compared degree programs and the gap between knowledge and action call for an individual but consistent implementation of the topics of climate change and environmental protection in the curriculum in all investigated degree courses. With the knowledge and awareness gained in this way, academics as distinguished members of society can convey climate awareness and fulfill the function as a role model.

A hidden curriculum for environmental topics in medical education: Impact on environmental knowledge and awareness of the students

Objective

Climate change constitutes a major challenge. The higher education sector plays an important role in regard to climate change and the adaptation to its consequences. Various approaches toward the integration of environmental subject areas to higher education teaching have already been described in other studies, but there is a lack of data supporting the effectiveness of these approaches in changing not only the environmental knowledge of students, but also their awareness. To address this, the present study tracked whether student attitudes about the environment could be changed by implicitly addressing medically relevant environmental topics as part of an online seminar.

Methods

Second semester students of molecular medicine attending a mandatory 14-hour online seminar, which was required to obtain additive key qualifications and which consisted of independent study phases as well as online class meetings, were divided into two groups: the intervention group (IG, n=27, thereof 20 in the pretest and 21 in the posttest) was exposed to medically relevant environmental topics, while the comparison group (CG, n=26, thereof 22 in the pretest and 21 in the posttest) was exposed to general, non-environmental medical topics. Surveys were conducted with standardized questionnaires before and after the seminar in order to study the influence on the students' environmental knowledge, awareness and other personal attitudes.

Results

While the seminar did not significantly change the environmental awareness in either group, the environmental knowledge of the IG was significantly increased by the group's exposure to environmental topics. In addition, the IG assessed its own environmental awareness regarding sustainable working methods in a laboratory as significantly higher after the seminar than the CG did, and some students of the IG had become more interested in issues relating to sustainability.

Conclusion

The approach used to communicate environmental content mainly increased the environmental knowledge of students and piqued the interest of some students in climate-related and environmental topics. However, it was not possible to change deeper personal attitudes about environmental awareness, especially everyday behavior.

Climate change and health: Changes in student environmental knowledge and awareness due to the implementation of a mandatory elective at the Medical Faculty of Ulm?

Background and objectives

According to the World Health Organization, climate change constitutes the single greatest threat to human health. However, the health care system contributes to climate change worldwide through its high CO₂ emissions. In order to make future physicians more aware of this issue and to expand medical education to include climate-related aspects, the mandatory 28 academic hours elective "Climate Change and Health" for students of human medicine in the preclinical study stage was implemented at the Medical Faculty of Ulm in the 2020/21 winter semester. Our accompanying study investigated 1. in what form the topic of climate change can be successfully integrated into the study of human medicine in a manner that includes student opinions and2. whether being required to take an elective on the topic led to changes in student environmental knowledge and awareness.

Methodology

Personal individual interviews were conducted with all n=11 students after the course in a pilot that was carried out in the 2020/21 winter semester to determine course feasibility and student acceptance. The students were also able to evaluate the course using an evaluation form and were asked to complete a questionnaire on their environmental knowledge and awareness before and after the course. The course was revised on the basis of the results and offered again in the 2021 summer semester with an intervention group (n=16, participation in the mandatory elective) and a comparison group (n=25, no participation in the mandatory elective). The intervention group was asked to evaluate the course on the evaluation form. Both groups completed the environmental questionnaire at the same time.

Results

The positive feedback from students for both semesters indicates a good feasibility and acceptance of the course. Student environmental knowledge was increased in both semesters. However, there were only few observable changes in student environmental awareness.

Conclusion

This paper illustrates how the topic of climate change and health can be embedded into medical studies. The students considered climate change an important topic and drew added value from the course for their future work in healthcare. The study shows that knowledge transfer at the university level is an effective way to educate the young generation on climate change and its impacts.

The neonicotinoid thiacloprid leads to multiple defects during early embryogenesis of the South African clawed frog (Xenopuslaevis)

There is increasing concern about the health effects of pesticides that pollute natural waters. In particular, the use of neonicotinoids, such as thiacloprid (THD), is causing unease. THD is considered non-toxic to non-target vertebrates. Studies classify THD as carcinogenic, toxic to reproduction, and therefore harmful to the environment. A detailed study of possible THD effects during the amphibian embryogenesis is needed because leaching can introduce THD into aquatic environments. We incubated stage 2 embryos of the South African clawed frog in various THD concentrations (0.1-100 mg/L) at 14 °C to study the potential effects of a one-time THD contamination of waters on the early embryogenesis. We showed that THD has, indeed, negative effects on the embryonic development of the X. laevis. A treatment with THD led to a reduced embryonic body length and mobility. Furthermore, a treatment with THD resulted in smaller cranial cartilages, eyes and brains, and the embryos had shorter cranial nerves and an impaired cardiogenesis. On a molecular basis, THD led to a reduced expression of the brain marker emx1 and the heart marker mhcα. Our results underly the importance of a strict and efficient monitoring of the regulatory levels and application areas of THD.

[The Climate Change Challenge: How to get research into society through an online workshop]

BACKGROUND

According to the World Health Organisation, climate change poses the greatest health threat to humanity. At the same time, an environmentally friendly lifestyle has a positive impact on our health, such as a plant-based diet. In order to counter climate change, society needs to be informed about climate-friendly and health-promoting measures. Therefore, an online workshop was initiated at the Medical Faculty of Ulm. In an accompanying study, it was determined whether this leads to changes in environmental knowledge and awareness among the participants.

METHODS

The online workshop consisted of four 2-hour sessions. Scientific basics on climate change and possible solutions were discussed. Other focuses were on health and the health system as well as environmental psychology and climate change denial. Participants could take part in an anonymous and voluntary online survey before (pretest) and after (posttest) the workshop.

RESULTS

86 participants took part in the workshop, of whom 24 attended all appointments and completed both surveys. While hardly any changes were observed in the subsection of environmental emotion, perception and behavior, there was a significant increase in environmental knowledge in the posttest. The workshop was evaluated very positively. Furthermore, many participants were motivated to make a personal contribution to climate protection after the workshop.

CONCLUSION

The workshop serves as a good example of how medical scientific findings can be shared at a societal level. The participants already showed a high level of environmental awareness in the pretest, which is why the question remains open as to how people can be sensitized to the (health) threats posed by climate change who do not proactively sign up for such an offer themselves.

Functional characterization of a novel TP53RK mutation identified in a family with Galloway-Mowat syndrome

Galloway-Mowat syndrome (GAMOS) is a very rare condition characterized by early-onset nephrotic syndrome and microcephaly with variable neurologic features. While considerable genetic heterogeneity of GAMOS has been identified, the majority of cases are caused by pathogenic variants in genes encoding the four components of the Kinase, endopeptidase, and other proteins of small size (KEOPS) complex, one of which is TP53RK. Here we describe a 3-year-old male with progressive microcephaly, neurodevelopmental deficits, and glomerular proteinuria. He was found to carry a novel homozygous TP53RK missense variant, c.163C>G (p.Arg55Gly), which was considered as potentially disease-causing. We generated a morpholino tp53rk knockdown model in Xenopus laevis showing that the depletion of endogenous Tp53rk caused abnormal eye and head development. This phenotype could be rescued by the expression of human wildtype TP53RK but not by the c.163C>G mutant nor by another previously described GAMOS-associated mutant c.125G>A (p.Gly42Asp). These findings support the pathogenic role of the novel TP53RK variant.

Environmental issues hidden in medical education: What are the effects on students' environmental awareness and knowledge?

INTRODUCTION

Global warming is one of the major challenges faced by society. To raise students' awareness related to these issues, we embedded environmental learning goals in mandatory courses. The aim of this initiative was to determine whether the integration of environmental topics into a seminar focussing on non-environmental issues facilitates changes in the environmental knowledge and awareness of students.

METHODS

Third-year molecular medicine students (intervention group, IG) were assigned short environment-related tasks in a not environment-related scientific writing seminar. Using standardized questionnaires before and after the seminar, students were assessed with a set of up to 48 questions relating to environmental affect, cognition, behavioral intention and knowledge as well as specific personal aspects. The comparison group (CG) consisted of third-year dentistry students who were assessed twice during an equivalent pre-post time period and who did not attend the seminar. The analysis was carried out with 15 students from the IG and 14 from the CG.

RESULTS

Integrating environmental topics into a scientific writing seminar focussing on non-environmental issues led to a significantly increased level of awareness of the threats from climate change in the IG (p<0.05). No further significant changes in other areas of environmental awareness were observed in either group. In addition, the environmental knowledge of the IG students (p≤0.01) but not of the CG students (p=0.285) was significantly enhanced.

DISCUSSION AND CONCLUSION

This study shows that factual environmental knowledge on the issues addressed can be increased by a cautious approach of environmental communication. However, more deep-seated personal attitudes and environmental awareness cannot be sustainably changed using this low intervention dose.

From the inverted classroom to the online lecture hall: Effects on students' satisfaction and exam results

On-site teaching at Ulm University was restricted in the summer semester (SS) 2020 due to the Corona pandemic. The biochemistry seminar "From gene to protein" in the 2nd preclinical semester, which had been successfully conducted as an Inverted Classroom (IC), had to be changed to an online concept. The aim of this study was to analyze the concept conversion in terms of students' satisfaction and knowledge acquisition. In the seminar, human medical students of the 2nd semester acquired biochemical and competency-oriented learning content. In SS2019, the course was taught using the IC concept. For the conversion to the online format in the SS2020, alternative teaching materials were developed and used. Students' satisfaction was assessed by an evaluation questionnaire and knowledge acquisition was tested by a written biochemistry exam. For both teaching concepts a high level of satisfaction was detected. Individual evaluation criteria were evaluated similarly by the students for both concepts. The online concept led up to significantly higher biochemistry exam scores. Due to the high levels of students' satisfaction in both concepts and the results of the biochemistry exam, it can be concluded that online teaching offers a suitable substitute. Based on these results, it is worth to undertake further research on digitization of studies.

Medical dissertation basics: analysis of a course of study for medical students

Background

Although the majority of medical students in Germany pursue a doctorate, only a portion of them receive a standardized scientific training, which is reflected in the quality issues seen in medical doctoral theses. The course Medical Dissertation Basics was conceptualized and scientifically monitored in order to support medical doctoral students on the one hand and to improve the quality of their scientific work on the other.

Methodology

The course consists of three modules. Module I, which is an introductory module, covers time and writing management and addresses how to approach literature and the principles of scientific work as well as the chapters required in a dissertation and the dissertation presentation and defense. In the practical module II, doctoral students write sections of their dissertation chapters and receive feedback via peer and expert reviews. Module III includes training on dissertation presentations and their defense. For objective analysis purposes, a multiple-choice test was administered before and after module I. Medical students from semesters 2 to 6 served as a control group. Questionnaires were used to subjectively analyze the training and support functions of modules I-III.

Results

High participation rates and the fact that the modules were taught numerous times show that doctoral students accept the courses. The objective analysis of module I showed a highly significant knowledge acquisition of the course group (N=55) in contrast to the control group (N=34). The doctoral students rated the course modules I-III with grades between 1.0 and 1.25 (grade A+/A; N=20-65 SD=0-0.44), felt well supported and estimated their learning success as high.

Conclusion

The study indicates knowledge acquisition in module I and a high doctoral student satisfaction with all modules. For an objective analysis of modules II-III, a comparison of completed doctoral theses (course participants vs. non-participants) would be appropriate but would only make sense in a few years. Based on the results of our study, we recommend that other faculties implement similar courses.

The Ribosomal Protein L5 Functions During Xenopus Anterior Development Through Apoptotic Pathways

Ribosomal biogenesis is a fundamental process necessary for cell growth and division. Ribosomal protein L5 (Rpl5) is part of the large ribosomal subunit. Mutations in this protein have been associated with the congenital disease Diamond Blackfan anemia (DBA), a so called ribosomopathy. Despite of the ubiquitous need of ribosomes, clinical manifestations of DBA include tissue-specific symptoms, e.g., craniofacial malformations, eye abnormalities, skin pigmentation failure, cardiac defects or liver cirrhosis. Here, we made use of the vertebrate model organism Xenopus laevis and showed a specific expression of rpl5 in the developing anterior tissue correlating with tissues affected in ribosomopathies. Upon Rpl5 knockdown using an antisense-based morpholino oligonucleotide approach, we showed different phenotypes affecting anterior tissue, i.e., defective cranial cartilage, malformed eyes, and microcephaly. Hence, the observed phenotypes in Xenopus laevis resemble the clinical manifestations of DBA. Analyses of the underlying molecular basis revealed that the expression of several marker genes of neural crest, eye, and brain are decreased during induction and differentiation of the respective tissue. Furthermore, Rpl5 knockdown led to decreased cell proliferation and increased cell apoptosis during early embryogenesis. Investigating the molecular mechanisms underlying Rpl5 function revealed a more than additive effect between either loss of function of Rpl5 and loss of function of c-Myc or loss of function of Rpl5 and gain of function of Tp53, suggesting a common signaling pathway of these proteins. The co-injection of the apoptosis blocking molecule Bcl2 resulted in a partial rescue of the eye phenotype, supporting the hypothesis that apoptosis is one main reason for the phenotypes occurring upon Rpl5 knockdown. With this study, we are able to shed more light on the still poorly understood molecular background of ribosomopathies.

Impact of glyphosate-based herbicide on early embryonic development of the amphibian Xenopus laevis

BACKGROUND

Worldwide, amphibian populations are declining drastically. One reason might be the use of pesticides including herbicides. The herbicide glyphosate is an inhibitor of the 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase of the plant shikimate pathway, preventing the formation of aromatic amino acids and thus inducing plant death. Due to this specific action, GBH are considered nontoxic to non-target organisms. However, GBH impairs embryonic development of chickens, amphibians and fishes. So far, no detailed tissue- and organ-specific analysis of the effects of GBH during development in amphibians has been performed.

RESULTS

We demonstrated that GBH Roundup® LB plus has a negative effect on embryonic development of the South African clawed frog Xenopus laevis. GBH treatment with sublethal concentrations resulted in a reduced body length and mobility of embryos. Furthermore, incubation with GBH led to smaller eyes, brains and cranial cartilages in comparison to untreated embryos. GBH incubation also resulted in shorter cranial nerves and had an effect on cardiac development including reduced heart rate and atrium size. On a molecular basis, GBH treatment led to reduced expression of marker genes in different tissues and developmental stages.

CONCLUSION

GBH leads to disturbed embryonic development of Xenopus laevis.

Galloway-Mowat syndrome: New insights from bioinformatics and expression during Xenopus embryogenesis

Galloway-Mowat syndrome (GAMOS) is a rare developmental disease. Patients suffer from congenital brain anomalies combined with renal abnormalities often resulting in an early-onset steroid-resistant nephrotic syndrome. The etiology of GAMOS has a heterogeneous genetic contribution. Mutations in more than 10 different genes have been reported in GAMOS patients. Among these are mutations in four genes encoding members of the human KEOPS (kinase, endopeptidase and other proteins of small size) complex, including OSGEP, TP53RK, TPRKB and LAGE3. Until now, these components have been functionally mainly investigated in bacteria, eukarya and archaea and in humans in the context of the discovery of its role in GAMOS, but the KEOPS complex members' expression and function during embryogenesis in vertebrates is still unknown. In this study, in silico analysis showed that both gene localization and the protein sequences of the three core KEOPS complex members Osgep, Tp53rk and Tprkb are highly conserved across different species including Xenopus laevis. In addition, we examined the spatio-temporal expression pattern of osgep, tp53rk and tprkb using RT-PCR and whole mount in situ hybridization approaches during early Xenopus development. We observed that all three genes were expressed during early embryogenesis and enriched in tissues and organs affected in GAMOS. More precisely, KEOPS complex genes are expressed in the pronephros, but also in neural tissue such as the developing brain, eye and cranial cartilage. These findings suggest that the KEOPS complex plays an important role during vertebrate embryonic development.

Mutations in PRDM15 Are a Novel Cause of Galloway-Mowat Syndrome

BACKGROUND

Galloway-Mowat syndrome (GAMOS) is characterized by neurodevelopmental defects and a progressive nephropathy, which typically manifests as steroid-resistant nephrotic syndrome. The prognosis of GAMOS is poor, and the majority of children progress to renal failure. The discovery of monogenic causes of GAMOS has uncovered molecular pathways involved in the pathogenesis of disease.

METHODS

Homozygosity mapping, whole-exome sequencing, and linkage analysis were used to identify mutations in four families with a GAMOS-like phenotype, and high-throughput PCR technology was applied to 91 individuals with GAMOS and 816 individuals with isolated nephrotic syndrome. In vitro and in vivo studies determined the functional significance of the mutations identified.

RESULTS

Three biallelic variants of the transcriptional regulator PRDM15 were detected in six families with proteinuric kidney disease. Four families with a variant in the protein's zinc-finger (ZNF) domain have additional GAMOS-like features, including brain anomalies, cardiac defects, and skeletal defects. All variants destabilize the PRDM15 protein, and the ZNF variant additionally interferes with transcriptional activation. Morpholino oligonucleotide-mediated knockdown of Prdm15 in Xenopus embryos disrupted pronephric development. Human wild-type PRDM15 RNA rescued the disruption, but the three PRDM15 variants did not. Finally, CRISPR-mediated knockout of PRDM15 in human podocytes led to dysregulation of several renal developmental genes.

CONCLUSIONS

Variants in PRDM15 can cause either isolated nephrotic syndrome or a GAMOS-type syndrome on an allelic basis. PRDM15 regulates multiple developmental kidney genes, and is likely to play an essential role in renal development in humans.

Retinol binding protein 1 affects Xenopus anterior neural development via all-trans retinoic acid signaling

BACKGROUND

Retinol binding protein 1 (Rbp1) acts as an intracellular regulator of vitamin A metabolism and retinoid transport. In mice, Rbp1 deficiency decreases the capacity of hepatic stellate cells to take up all-trans retinol and sustain retinyl ester stores. Furthermore, Rbp1 is crucial for visual capacity. Although the function of Rbp1 has been studied in the mature eye, its role during early anterior neural development has not yet been investigated in detail.

RESULTS

We showed that rbp1 is expressed in the eye, anterior neural crest cells (NCCs) and prosencephalon of the South African clawed frog Xenopus laevis. Rbp1 knockdown led to defects in eye formation, including microphthalmia and disorganized retinal lamination, and to disturbed induction and differentiation of the eye field, as shown by decreased rax and pax6 expression. Furthermore, it resulted in reduced rax expression in the prosencephalon and affected cranial cartilage. Rbp1 inhibition also interfered with neural crest induction and migration, as shown by twist and slug. Moreover, it led to a significant reduction of the all-trans retinoic acid target gene pitx2 in NCC-derived periocular mesenchyme. The Rbp1 knockdown phenotypes were rescued by pitx2 RNA co-injection.

CONCLUSION

Rbp1 is crucial for the development of the anterior neural tissue.

Longitudinal curriculum development: gradual optimization of a biochemistry seminar

Objective: The Master Plan for Medical Studies 2020 places additional emphasis on curricular development processes. In addition, institutes may recognize a need to optimize their courses, for example because of poor evaluations. Frequently, however, the resources required for comprehensive optimizations are not available. In the present study, we aimed to use the example of a biochemistry seminar that takes place in the preclinical part of the medical degree at Ulm University Medical School to show how a course can be successfully optimized in small steps and evaluation results can be used for quality assurance. Methods: Similar to a continuous improvement process (CIP), over the course of five years a biochemistry seminar was gradually optimized in three steps. This process used structural, methodological, and content components, such as vertical integration, the inverted classroom method, and competence orientation. For quality assurance, we analyzed the official, standardized evaluation sheets from a total of n=1248 students. We evaluated the optimization process on the basis of responses to evaluation statements that were arranged into categories such as "organization, structure, implementation" and "quality of teaching," free text information, and the results of a pilot study conducted in parallel. We then determined the usefulness of the students' evaluation results for evaluating the optimization process. Results: Each developmental step resulted in a significantly more positive overall evaluation of the seminar by the students. This result was independent of whether the development was on a structural or methodological/content-related level. In addition, the evaluations of the categories that were optimized were significantly better. For example, the vertical integration and introduction of the inverted classroom method were accompanied by a better evaluation of the "quality of teaching" and a change in the structure led to a higher score in the category "organization, structure, implementation." A comparison with the free text evaluation sheets and the results of the pilot study supports the results. Conclusion: Although optimization of a curriculum or course is a major task, it can also be successfully completed in small steps. With this approach, new learning goals, for example as required in the Master Plan for Medical Studies 2020, can be continuously integrated and student satisfaction with a course can be increased. Student evaluation results can represent a kind of quality assurance in this process and can provide important impulses for optimization.

Utilizing research findings in medical education: The testing effect within a flipped/inverted biochemistry classroom

Purpose: Basic research about test-enhanced learning points towards its effectiveness to improve students' learning and is still underutilized in educational practice. Therefore, we developed an evidence-based instructional design to investigate the usefulness of test-enhanced learning within a flipped/inverted classroom approach. Materials and Methods: We developed two modes of learning material for the self-study phase of a flipped classroom for 139 students: in addition to educational films, one group of students received a reader and another group received multiple-choice questions that corresponded to the reader in content and length. An assessment of the content of the learning material was conducted at the subsequent on-site phase. Also, ratings about students' perceptions of the additional learning material were gathered. Results: At the assessment, students that prepared with films and multiple-choice questions outperformed students that prepared with films and the reader. Furthermore, students perceived the multiple-choice questions as more helpful, more motivating and felt better prepared for the assessment than students that used the reader. Conclusions: This study shows that test-enhanced learning can be utilized to promote students' learning within the self-study phase of a flipped classroom. Not only assessment scores are positively affected but also the motivation to learn and preparedness towards an assessment.

Investigating the self-study phase of an inverted biochemistry classroom - collaborative dyadic learning makes the difference

BACKGROUND

The inverted classroom approach is characterized by a primary self-study phase for students followed by an on-site, face-to-face teaching phase that is used to deepen the prior acquired knowledge. Obviously, this teaching approach relies on the students preparing before the on-site phase, which in turn requires optimized preparatory material as well as defined working instructions. The major aim of this study, therefore, was to investigate the effect of different preparatory materials and working instructions for the self-study phase of an e-learning-based inverted classroom on the knowledge gained by medical students in biochemistry. Furthermore, we analyzed whether collaborative dyadic learning during the self-study phase is more effective than individual learning with respect to knowledge gain.

METHODS

The study was performed in a biochemistry seminar for second semester medical students at Ulm University in Germany. This seminar was held using an e-learning-based inverted classroom. A total of 196 students were divided into three homogeneous study groups that differed in terms of the working material and instructions provided for the self-study phase. Knowledge gain was measured by formative tests at the beginning of the on-site phases. Questionnaires were also handed out asking about motivation, interest and learning time in the self-study phases.

RESULTS

Students who were told to prepare in collaborating dyads during the self-study phase performed better in formative tests taken at the beginning of on-site phases than learners who were told to prepare individually. The study material that was provided was of minor importance for the differences in formative testing since almost all students prepared for the on-site phases. With the dyadic learning approach, both students benefited from this collaboration, characterized by a higher motivation and interest in the topic, as well as a longer time spent on task.

CONCLUSION

Our study provides strong evidence that the study material, but more importantly the instructions provided for the self-study phase, affect students` knowledge gain in an e-learning-based inverted classroom. The instructed collaboratively working group was the most successful.

The Wnt inhibitor Dkk1 is required for maintaining the normal cardiac differentiation program in Xenopus laevis

Wnt proteins can activate different intracellular signaling pathways. These pathways need to be tightly regulated for proper cardiogenesis. The canonical Wnt/β-catenin inhibitor Dkk1 has been shown to be sufficient to trigger cardiogenesis in gain-of-function experiments performed in multiple model systems. Loss-of-function studies however did not reveal any fundamental function for Dkk1 during cardiogenesis. Using Xenopus laevis as a model we here show for the first time that Dkk1 is required for proper differentiation of cardiomyocytes, whereas specification of cardiomyocytes remains unaffected in absence of Dkk1. This effect is at least in part mediated through regulation of non-canonical Wnt signaling via Wnt11. In line with these observations we also found that Isl1, a critical regulator for specification of the common cardiac progenitor cell (CPC) population, acts upstream of Dkk1.

•

Dkk1 is required for cardiac development in Xenopus laevis.

•

The Wnt inhibitor Dkk1 acts downstream of Isl1 during cardiac development in vivo.

•

Loss of Dkk1 has no impact on cardiac specification in Xenopus.

•

Normal cardiac differentiation is impaired upon Dkk1 inhibition in Xenopus.

•

Dkk1 regulates canonical Wnt/β-catenin signaling during Xenopus cardiogenesis.

Nosip functions during vertebrate eye and cranial cartilage development

BACKGROUND

The nitric oxide synthase interacting protein (Nosip) has been associated with diverse human diseases including psychological disorders. In line, early neurogenesis of mouse and Xenopus is impaired upon Nosip deficiency. Nosip knockout mice show craniofacial defects and the down-regulation of Nosip in the mouse and Xenopus leads to microcephaly. Until now, the exact underlying molecular mechanisms of these malformations were still unknown.

RESULTS

Here, we show that nosip is expressed in the developing ocular system as well as the anterior neural crest cells of Xenopus laevis. Furthermore, Nosip inhibition causes severe defects in eye formation in the mouse and Xenopus. Retinal lamination as well as dorso-ventral patterning of the retina were affected in Nosip-depleted Xenopus embryos. Marker gene analysis using rax, pax6 and otx2 reveals an interference with the eye field induction and differentiation. A closer look on Nosip-deficient Xenopus embryos furthermore reveals disrupted cranial cartilage structures and an inhibition of anterior neural crest cell induction and migration shown by twist, snai2, and egr2. Moreover, foxc1 as downstream factor of retinoic acid signalling is affected upon Nosip deficiency.

CONCLUSIONS

Nosip is a crucial factor for the development of anterior neural tissue such the eyes and neural crest cells. Developmental Dynamics 247:1070-1082, 2018. © 2018 Wiley Periodicals, Inc.

Concept and benefits of the Inverted Classroom method for a competency-based biochemistry course in the pre-clinical stage of a human medicine course of studies

Background: Medical students often have a problem recognising the relevance of basic science subjects for their later professional work in the pre-clinical stage of their studies. This can lead to a lower motivation to learn biochemical content and dissatisfaction in the courses amongst the students. Alternative teaching methods such as the Inverted Classroom (IC) method can address this deficiency. The goal of this study was: to analyse the motivation and satisfaction of the students in a biochemistry seminar through the use of the e-learning-based IC method, to investigate the acceptance against the IC teaching method in biochemistry, and to compare the learning success achieved using the IC approach with that of a traditional course. We also investigated how a biochemistry course in the pre-clinical stage of a human medicine course of studies can be successfully organised according to the IC method. Furthermore, we examined the benefits of the IC method over conventional teaching formats. Method: The IC method was implemented in accordance with the guidelines of the GMA committee "New Media" [30] in a biochemistry seminar for two student IC intervention groups with 42 students. A part of the factual knowledge from the on-site phase in the form of teaching videos together with self-learning control tasks were provided online before the seminar for both IC intervention groups. Exporting content to the self-learning phase creates new free time in the on-site phase, during which the content can be critically considered and processed and additional competency-based learning objectives can be taught. Identical biochemistry teaching content was taught in parallel control groups (14 student groups with n=299 students), but no material was handed out beforehand for a self-learning phase. These students only received the materials after the on-site phase. Motivation and satisfaction as well as the acceptance for the teaching methods were recorded by questionnaires, the acquisition of knowledge by MC exams. Results: On a Likert scale from 1 (strongly disagree) to 6 (strongly agree), the students in the IC intervention groups could be seen to be much more motivated (5.53) than students in the control group (4.01). Students in the IC intervention groups also recognised the relevance of the learning content much more clearly (5.44) than students in the control group (4.01). Furthermore, the IC group also observed that additional competencies were trained in addition to the biochemistry content. In addition, the IC intervention group award the event a school grade of 1.53, the traditional control group a grade of 2.96. The teaching videos were rated very positively by both groups with an average school grade of 1.3 in each case. A qualitative analysis showed that the motivation and a positive attitude of the lecturers played a decisive role in the successful implementation of the IC method. Discussion and conclusion: Pre-clinical students display a high acceptance of the e-learning-based IC method. Teaching communication competencies in a biochemistry seminar was also rated very positively by the students. The quality of the teaching video and the motivation of the lecturers were shown to be a critical parameter for the successful performance of the IC method. What's more, the IC method can contribute to implementing a competence orientation in medical studies.

Frizzled 3 acts upstream of Alcam during embryonic eye development

Formation of a functional eye during vertebrate embryogenesis requires different processes such as cell differentiation, cell migration, cell-cell interactions as well as intracellular signalling processes. It was previously shown that the non-canonical Wnt receptor Frizzled 3 (Fzd3) is required for proper eye formation, however, the underlying mechanism is poorly understood. Here we demonstrate that loss of Fzd3 induces severe malformations of the developing eye and that this defect is phenocopied by loss of the activated leukocyte cell adhesion molecule (Alcam). Promoter analysis revealed the presence of a Fzd3 responsive element within the alcam promoter, which is responsible for alcam expression during anterior neural development. In-depth analysis identified the jun N-terminal protein kinase 1 (JNK1) and the transcription factor paired box 2 (Pax2) to be important for the activation of alcam expression. Altogether our study reveals that alcam is activated through non-canonical Wnt signalling during embryonic eye development in Xenopus laevis and shows that this pathway plays a similar role in different tissues.

The CapZ interacting protein Rcsd1 is required for cardiogenesis downstream of Wnt11a in Xenopus laevis

Wnt proteins are critical for embryonic cardiogenesis and cardiomyogenesis by regulating different intracellular signalling pathways. Whereas canonical Wnt/β-catenin signalling is required for mesoderm induction and proliferation of cardiac progenitor cells, β-catenin independent, non-canonical Wnt signalling regulates cardiac specification and terminal differentiation. Although the diverse cardiac malformations associated with the loss of non-canonical Wnt11 in mice such as outflow tract (OFT) defects, reduced ventricular trabeculation, myofibrillar disorganization and reduced cardiac marker gene expression are well described, the underlying molecular mechanisms are still not completely understood. Here we aimed to further characterize Wnt11 mediated signal transduction during vertebrate cardiogenesis. Using Xenopus as a model system, we show by loss of function and corresponding rescue experiments that the non-canonical Wnt signalling mediator Rcsd1 is required downstream of Wnt11 for ventricular trabeculation, terminal differentiation of cardiomyocytes and cardiac morphogenesis. We here place Rcsd1 downstream of Wnt11 during cardiac development thereby providing a novel mechanism for how non-canonical Wnt signalling regulates vertebrate cardiogenesis.

Comparative expression analysis of cysteine-rich intestinal protein family members crip1, 2 and 3 during Xenopus laevis embryogenesis

Members of the cysteine-rich intestinal protein (Crip) family belong to the group 2 LIM proteins. Crip proteins are widely expressed in adult mammals but their expression profile and function during embryonic development are still mostly unknown. In this study, we have described for the first time the spatio-temporal expression pattern of the three family members crip1, crip2 and crip3 during Xenopus laevis embryogenesis by RT-PCR and whole mount in situ hybridization approaches. We observed that all three genes are expressed in the pronephros, branchial arches and the eye. Furthermore, crip1 transcripts could be visualized in the developing cranial ganglia and neural tube. In contrast, crip2 could be detected in the cardiovascular system, the brain and the neural tube while crip3 was expressed in the cranial ganglions and the heart. Based on these findings, we suggest that each crip family member may play an important role during embryonic development.

A phospho-dependent mechanism involving NCoR and KMT2D controls a permissive chromatin state at Notch target genes

The transcriptional shift from repression to activation of target genes is crucial for the fidelity of Notch responses through incompletely understood mechanisms that likely involve chromatin-based control. To activate silenced genes, repressive chromatin marks are removed and active marks must be acquired. Histone H3 lysine-4 (H3K4) demethylases are key chromatin modifiers that establish the repressive chromatin state at Notch target genes. However, the counteracting histone methyltransferase required for the active chromatin state remained elusive. Here, we show that the RBP-J interacting factor SHARP is not only able to interact with the NCoR corepressor complex, but also with the H3K4 methyltransferase KMT2D coactivator complex. KMT2D and NCoR compete for the C-terminal SPOC-domain of SHARP. We reveal that the SPOC-domain exclusively binds to phosphorylated NCoR. The balance between NCoR and KMT2D binding is shifted upon mutating the phosphorylation sites of NCoR or upon inhibition of the NCoR kinase CK2β. Furthermore, we show that the homologs of SHARP and KMT2D in Drosophila also physically interact and control Notch-mediated functions in vivo. Together, our findings reveal how signaling can fine-tune a committed chromatin state by phosphorylation of a pivotal chromatin-modifier.

Direct nkx2-5 transcriptional repression of isl1 controls cardiomyocyte subtype identity

During cardiogenesis, most myocytes arise from cardiac progenitors expressing the transcription factors Isl1 and Nkx2-5. Here, we show that a direct repression of Isl1 by Nkx2-5 is necessary for proper development of the ventricular myocardial lineage. Overexpression of Nkx2-5 in mouse embryonic stem cells (ESCs) delayed specification of cardiac progenitors and inhibited expression of Isl1 and its downstream targets in Isl1(+) precursors. Embryos deficient for Nkx2-5 in the Isl1(+) lineage failed to downregulate Isl1 protein in cardiomyocytes of the heart tube. We demonstrated that Nkx2-5 directly binds to an Isl1 enhancer and represses Isl1 transcriptional activity. Furthermore, we showed that overexpression of Isl1 does not prevent cardiac differentiation of ESCs and in Xenopus laevis embryos. Instead, it leads to enhanced specification of cardiac progenitors, earlier cardiac differentiation, and increased cardiomyocyte number. Functional and molecular characterization of Isl1-overexpressing cardiomyocytes revealed higher beating frequencies in both ESC-derived contracting areas and Xenopus Isl1-gain-of-function hearts, which associated with upregulation of nodal-specific genes and downregulation of transcripts of working myocardium. Immunocytochemistry of cardiomyocyte lineage-specific markers demonstrated a reduction of ventricular cells and an increase of cells expressing the pacemaker channel Hcn4. Finally, optical action potential imaging of single cardiomyocytes combined with pharmacological approaches proved that Isl1 overexpression in ESCs resulted in normally electrophysiologically functional cells, highly enriched in the nodal subtype at the expense of the ventricular lineage. Our findings provide an Isl1/Nkx2-5-mediated mechanism that coordinately regulates the specification of cardiac progenitors toward the different myocardial lineages and ensures proper acquisition of myocyte subtype identity.

An Epha4/Sipa1l3/Wnt pathway regulates eye development and lens maturation

The signal-induced proliferation associated family of proteins comprises four members, SIPA1 and SIPA1L1-1L3. Mutations of the human SIPA1L3 gene result in congenital cataracts. In Xenopus, loss of Sipa1l3 function led to a severe eye phenotype that was distinguished by smaller eyes and lenses including lens fiber cell maturation defects. We found a direct interaction between Sipa1l3 and Epha4, building a functional platform for proper ocular development. Epha4 deficiency phenocopied loss of Sipa1l3 and rescue experiments demonstrated that Epha4 acts up-stream of Sipa1l3 during eye development. Both, Sipa1l3 and Epha4 are required for early eye specification. The ocular phenotype, upon loss of either Epha4 or Sipa1l3, was partially mediated by rax. We demonstrated that canonical Wnt signaling is inhibited downstream of Epha4/Sipa1l3 during normal eye development. Depletion of either Sipa1l3 or Epha4 resulted in an up-regulation of axin2 expression, a direct Wnt/β-catenin target gene. In line with this, Sipa1l3 or Epha4 depletion could be rescued by blocking Wnt/β-catenin or activating non-canonical Wnt signaling. We therefore conclude that this pathomechanism prevents proper eye development and maturation of lens fiber cells resulting in congenital cataracts.

Deletions and de novo mutations of SOX11 are associated with a neurodevelopmental disorder with features of Coffin-Siris syndrome

BACKGROUND

SOX11 is a transcription factor proposed to play a role in brain development. The relevance of SOX11 to human developmental disorders was suggested by a recent report of SOX11 mutations in two patients with Coffin-Siris syndrome. Here we further investigate the role of SOX11 variants in neurodevelopmental disorders.

METHODS

We used array based comparative genomic hybridisation and trio exome sequencing to identify children with intellectual disability who have deletions or de novo point mutations disrupting SOX11. The pathogenicity of the SOX11 mutations was assessed using an in vitro gene expression reporter system. Loss-of-function experiments were performed in xenopus by knockdown of Sox11 expression.

RESULTS

We identified seven individuals with chromosome 2p25 deletions involving SOX11. Trio exome sequencing identified three de novo SOX11 variants, two missense (p.K50N; p.P120H) and one nonsense (p.C29*). The biological consequences of the missense mutations were assessed using an in vitro gene expression system. These individuals had microcephaly, developmental delay and shared dysmorphic features compatible with mild Coffin-Siris syndrome. To further investigate the function of SOX11, we knocked down the orthologous gene in xenopus. Morphants had significant reduction in head size compared with controls. This suggests that SOX11 loss of function can be associated with microcephaly.

CONCLUSIONS

We thus propose that SOX11 deletion or mutation can present with a Coffin-Siris phenotype.

Sipa1l3/SPAR3 is targeted to postsynaptic specializations and interacts with the Fezzin ProSAPiP1/Lzts3

Rap GTPase-activating proteins (RapGAPs) are essential for synaptic function as they tightly regulate synaptic Rap signaling. Among the most abundant synaptic RapGAPs in brain are the Spine-associated RapGAPs (SPARs) Sipa1l1/SPAR and Sipa1l2/SPAR2, whereas nothing has been reported on Sipa1l3/SPAR3. In this study, we show that Sipa1l3/SPAR3 is conserved across species, has a distinct expression pattern in the developing rat brain and is localized at excitatory postsynapses. We further demonstrate that the Sipa1l3/SPAR3 C-terminus is required for postsynaptic targeting and represents an interaction module for Fezzins such as ProSAPiP1/Lzts3, a binding partner of the postsynaptic scaffold protein Shank3. Taken together, our data imply that Sipa1l3/SPAR3 is a hitherto unknown synaptic RapGAP, which is targeted to postsynaptic specializations and interacts with Fezzins. Spine-associated RapGAPs (SPARs) are essential modulators of synaptic signaling. Our study is the first to characterize the SPAR family member Sipa1l3/SPAR3 in neuronal tissue. We show that Sipa1l3/SPAR3 is conserved across species, has a distinct expression pattern in brain and is localized to excitatory postsynapses via its C-terminus, which represents an interaction module for other postsynaptic proteins including the Fezzin ProSAPiP1/Lzts3.

The Wnt/JNK signaling target gene alcam is required for embryonic kidney development

Proper development of nephrons is essential for kidney function. β-Catenin-independent Wnt signaling through Fzd8, Inversin, Daam1, RhoA and Myosin is required for nephric tubule morphogenesis. Here, we provide a novel mechanism through which non-canonical Wnt signaling contributes to tubular development. Using Xenopus laevis as a model system, we found that the cell-adhesion molecule Alcam is required for proper nephrogenesis and functions downstream of Fzd3 during embryonic kidney development. We found alcam expression to be independent of Fzd8 or Inversin, but to be transcriptionally regulated by the β-Catenin-independent Wnt/JNK pathway involving ATF2 and Pax2 in a direct manner. These novel findings indicate that several branches of Wnt signaling are independently required for proximal tubule development. Moreover, our data indicate that regulation of morphogenesis by non-canonical Wnt ligands also involves direct transcriptional responses in addition to the effects on a post-translational level.

Comparative analysis reveals distinct and overlapping functions of Mef2c and Mef2d during cardiogenesis in Xenopus laevis

The family of vertebrate Mef2 transcription factors is comprised of four members named Mef2a, Mef2b, Mef2c, and Mef2d. These transcription factors are regulators of the myogenic programs with crucial roles in development of skeletal, cardiac and smooth muscle cells. Mef2a and Mef2c are essential for cardiac development in mice. In Xenopus, mef2c and mef2d but not mef2a were recently shown to be expressed during cardiogenesis. We here investigated the function of Mef2c and Mef2d during Xenopus laevis cardiogenesis. Knocking down either gene by corresponding antisense morpholino oligonucleotides led to profound heart defects including morphological abnormalities, pericardial edema, and brachycardia. Marker gene expression analyses and rescue experiments revealed that (i) both genes are required for proper cardiac gene expression, (ii) Mef2d can compensate for the loss of Mef2c but not vice versa, and (iii) the γ domain of Mef2c is required for early cardiac development. Taken together, our data provide novel insights into the function of Mef2 during cardiogenesis, highlight evolutionary differences between species and might have an impact on attempts of direct reprogramming.

Lypd6 enhances Wnt/β-catenin signaling by promoting Lrp6 phosphorylation in raft plasma membrane domains

Wnt/β-catenin signaling plays critical roles during embryogenesis, tissue homeostasis, and regeneration. How Wnt-receptor complex activity is regulated is not yet fully understood. Here, we identify the Ly6 family protein LY6/PLAUR domain-containing 6 (Lypd6) as a positive feedback regulator of Wnt/β-catenin signaling. lypd6 enhances Wnt signaling in zebrafish and Xenopus embryos and in mammalian cells, and it is required for wnt8-mediated patterning of the mesoderm and neuroectoderm during zebrafish gastrulation. Lypd6 is GPI anchored to the plasma membrane and physically interacts with the Wnt receptor Frizzled8 and the coreceptor Lrp6. Biophysical and biochemical evidence indicates that Lypd6 preferentially localizes to raft membrane domains, where Lrp6 is phosphorylated upon Wnt stimulation. lypd6 knockdown or mislocalization of the Lypd6 protein to nonraft membrane domains shifts Lrp6 phosphorylation to these domains and inhibits Wnt signaling. Thus, Lypd6 appears to control Lrp6 activation specifically in membrane rafts, which is essential for downstream signaling.

The Nedd4-binding protein 3 (N4BP3) is crucial for axonal and dendritic branching in developing neurons

Background

Circuit formation in the nervous system essentially relies on the proper development of neurons and their processes. In this context, the ubiquitin ligase Nedd4 is a crucial modulator of axonal and dendritic branching.

Results

Herein we characterize the Nedd4-binding protein 3 (N4BP3), a Fezzin family member, during nerve cell development. In developing rat primary hippocampal neurons, endogenous N4BP3 localizes to neuronal processes, including axons and dendrites. Transient in vitro knockdown of N4BP3 in hippocampal cultures during neuritogenesis results in impaired branching of axons and dendrites. In line with these findings, in vivo knockdown of n4bp3 in Xenopus laevis embryos results in severe alteration of cranial nerve branching.

Conclusions

We introduce N4BP3 as a novel molecular element for the correct branching of neurites in developing neurons and propose a central role for an N4BP3-Nedd4 complex in neurite branching and circuit formation.

sox4 and sox11 function during Xenopus laevis eye development

SoxC genes are involved in many developmental processes such as cardiac, lymphoid, and bone development. The SoxC gene family is represented by Sox4, Sox11, and Sox12. Loss of either Sox4 or Sox11 function is lethal during mouse embryogenesis. Here, we demonstrate that sox4 and sox11 are strongly expressed in the developing eye, heart as well as brain in Xenopus laevis. Morpholino oligonucleotide mediated knock-down approaches in anterior neural tissue revealed that interference with either Sox4 or Sox11 function affects eye development. A detailed analysis demonstrated strong effects on eye size and retinal lamination. Neural induction was unaffected upon Sox4 or Sox11 MO injection and early eye field differentiation and cell proliferation were only mildly affected. Depletion of both genes, however, led independently to a significant increase in cell apoptosis in the eye. In summary, Sox4 and Sox11 are required for Xenopus visual system development.

Tbx5 overexpression favors a first heart field lineage in murine embryonic stem cells and in Xenopus laevis embryos

The T-box transcription factor Tbx5 is involved in several developmental processes including cardiogenesis. Early steps of cardiac development are characterised by the formation of two cardiogenic lineages, the first (FHF) and the second heart field (SHF) lineage, which arise from a common cardiac progenitor cell population. To further investigate the function of Tbx5 during cardiogenesis, we generated a murine embryonic stem cell line constitutively overexpressing Tbx5. Differentiation of these cells is characterised by an earlier and increased appearance of contracting cardiomyocytes that beat with a higher frequency than control cells. In semi-quantitative and quantitative RT-PCR analyses, we observed an up-regulation of cardiac marker genes such as Troponin T, endogenous Tbx5, and Nkx2.5 and a down-regulation of others like BMP4 and Hand2. Similar data were gained in Xenopus laevis arguing for a conserved function of Tbx5. Furthermore, markers of the conduction system and atrial cardiomyocytes were increased.

Improving cardiac regeneration after injury: are we a step closer?

During regeneration, lost functional tissue can, in general, be replaced by different mechanisms, including proliferation of terminally differentiated cells or through differentiation of resident stem cells. It is a well-accepted dogma that the mammalian heart cannot efficiently regenerate upon injury as a consequence of insufficient oxygen supply. This is in sharp contrast to the hearts of adult zebrafish or newts that are able to replace lost ventricular tissue. Novel data indicate that the young murine heart also has the ability to regenerate within the first week after birth using mechanisms apparently quite similar to those observed in fish. This now provides us with a good starting point to identify the molecular mechanisms that led to the loss of the regenerative capacity of the adult mammalian heart. These future studies will also indicate whether it will be possible to reawaken the regenerative capability of cardiomyocytes in the human heart by treatment with selected pharmaceuticals.