A genome resource for the marine annelid Platynereis dumerilii.

The marine annelid Platynereis dumerilii is a model organism used in many research areas including evolution and development, neurobiology, ecology and regeneration. Here we present the genomes of P. dumerilii and of the closely related P. massiliensis and P. megalops , to facilitate comparative genomic approaches and help explore Platynereis biology. We used long-read sequencing technology and chromosomal-conformation capture along with extensive transcriptomic resources to obtain and annotate a draft genome assembly of ∼1.47 Gbp for P. dumerilii , of which more than half represent repeat elements. We predict around 29,000 protein-coding genes, with relatively large intron sizes, over 38,000 non-coding genes, and 580 miRNA loci. We further explore the high genetic variation (∼3% heterozygosity) within the Platynereis species complex. Gene ontology reveals the most variable loci to be associated with pigmentation, development and immunity. The current work sets the stage for further development of Platynereis genomic resources.

Family Club Denmark: A Quasi-Randomized Study of a Volunteer-Based Intervention to Support Vulnerable Families.

Volunteer interventions play a vital role in supporting families by offering accessible and community-based resources outside the formal professional sector. This study examines the impact of the volunteer intervention known as Family Club Denmark (FCD) on the well-being of parents and children. FCD aims to provide families with positive experiences and support relationship building. The intervention, open to families from diverse social backgrounds, comprises volunteer-led family clubs where parents and children aged 2-12 years engage in activities and meals. We allocated 510 families (363 vulnerable families) to FCD or placed them on a waiting list based on a first-come, first-served principle. We conducted baseline, post-intervention, and follow-up assessments through questionnaires, observations, and interviews. On average, families participated in 5.8 sessions, with both families and volunteers reporting high satisfaction. When compared to control families, we find that vulnerable FCD parents feel more confident playing with their children (p = 0.04, [0.01; 0.40], d = 0.25), require less assistance in playing with their children (p = 0.01, [-0.34; -0.05], d = 0.33), and report that their children have a more challenging time forming friendships (p = 0.01, [-0.51; -0.09], d = 0.29). However, we did not find significant effects on mental health, parenting stress, self-efficacy, self-worth, family routines, or child well-being. We observed similar results for the full sample. The discovery that parents feel more confident playing with their children after participating in FCD highlights the vital role of volunteer-based interventions in enhancing parental engagement and fostering positive parent-child interactions. Trial registration: ClinicalTrials.gov NCT03657888 (registered 29 August 2018).

Effects on Child Development and Parent-Child Interaction of the FACAM Intervention: A Randomized Controlled Study of an Interdisciplinary Intervention to Support Women in Vulnerable Positions through Pregnancy and Early Motherhood.

Health inequality can have a profound impact on a child's life. Maternal mental health challenges can hinder bonding, leading to impaired functioning and poorer child outcomes. To provide extra support for vulnerable pregnant women, the FACAM intervention offers the services of a health nurse or family therapist from pregnancy until the child starts school. This study examined the effects of FACAM intervention on pregnant women in vulnerable positions and their children until the child turned two years old. We randomly assigned 331 pregnant women to either FACAM intervention or care as usual and assessed them at baseline and when the infant was 3-6, 12-13.5, and 24 months old. The primary outcome was maternal sensitivity measured by Coding Interactive Behavior (CIB). Secondary outcomes included the parent-child relationship, child social-emotional development, child developmental progress, parent-child interaction, and child development. Our findings indicate that care-as-usual children were significantly more involved than FACAM children when the child was 4-6 months old (b = -0.25, [-0.42; -0.08] d = -0.42). However, we suspect this result is due to a biased dropout. We did not find any significant differences in any other outcomes. Therefore, the study suggests that the FACAM intervention is not superior to care as usual regarding child development and parent-child interaction outcomes.

Parent-child Relationship Outcomes of the Incredible Years Parents and Babies Program: A Pilot Randomized Controlled Trial.

Background: A warm, sensitive, and responsive relationship to a caregiver is essential for healthy child development. Objective: This paper examines the effects of the Incredible Years Parents and Babies (IYPB) program on the parent-child relationship at post-intervention when offered as a universal parenting intervention to parents with newborn infants. Method: We conducted a pragmatic, two-arm, parallel pilot randomized controlled trial; 112 families with newborns were randomized to IYPB intervention (76) or usual care (36). The IYPB program is a group intervention with eight two-hour sessions. In addition to parent-reported questionnaires, we collected a six-minute-long video at post-intervention from 97 families to assess the parent-child relationship, which was then coded with the Coding Interactive Behavior system. Results: There were no significant intervention effects on either the total score or any of the seven subscales at post-intervention when the children were around 5.5 months old. For parental sensitivity, results were significant at the 10% level, favoring the IYPB group. When examining the lowest-functioning mothers in moderator analyses, we also found no significant differences between the two groups. Conclusion: In line with parent-report outcomes, we did not find any statistically significant differences between the IYPB program and usual care on parent-child relationship when offered as a universal intervention for a relatively well-functioning group of parents with infants in a setting with a high standard of usual care. However, there was a positive trend for the total score, parental sensitivity and reciprocity with effect sizes in the range of .41-.51. It is possible that a larger sample would have resulted in significant differences for these outcomes. Trial registration: ClinicalTrials.gov NCT01931917 (registration date August 27, 2013).

Minding the Baby versus usual care: study protocol for a quasi-cluster-randomized controlled study in Denmark of an early interdisciplinary home-visiting intervention for families at increased risk for adversity.

BACKGROUND: Inequality in health can have profound effects on a child's opportunities later in life. To prevent these downstream effects in families at increased risk of adversity, programs are needed to provide support and improve well-being across several domains. The present trial is aimed at assessing the effectiveness of the Minding the Baby® (MTB) home visiting intervention in improving the mother-child relationship, parental reflective functioning, well-being, and mental health, as well as child development and well-being in families at known risk of adverse health, relational, and developmental outcomes. METHODS: The study is a pragmatic, prospective, quasi-cluster-randomized controlled trial in which seven Danish municipalities were randomized to MTB training in either 2018 or 2019. A total of 250 pregnant women at increased risk of adversity will be recruited (75 care as usual families and 175 intervention families). Care as usual families will be recruited before and after the MTB training. The MTB intervention is an attachment-based, interdisciplinary home visiting intervention offered from the third trimester of pregnancy until the child is 2 years old. The participants are assessed at baseline, and when the infant is 3, 12, and 24 months old. The primary outcome is maternal sensitivity measured by the Coding Interactive Behavior scale applied to video recordings of mother-infant interactions. Secondary outcomes include parent-child interaction, parental reflective functioning, parental mental health, maternal satisfaction, parental stress, and child development and well-being. The treatment effect is estimated as a fixed effect using a binary indicator of MTB treatment, and cluster-robust standard errors based on wild bootstrap are used for inference. DISCUSSION: This is the first trial of MTB in a Scandinavian context and will include the largest sample yet in a trial of MTB. The trial is expected to contribute to knowledge about the effect of early support for pregnant women, their infants, and their families at increased risk of adversity. TRIAL REGISTRATION: ClinicalTrials.gov NCT03495895 . The study was registered on April 12, 2018.

The FACAM study: protocol for a randomized controlled study of an early interdisciplinary intervention to support women in vulnerable positions through pregnancy and the first 5 years of motherhood.

BACKGROUND: Inequality in health can have profound short- and long-term effects on a child's life. Infants develop in a responsive environment, and the relationship between mother and infant begins to develop during pregnancy. The mother's ability to bond with the fetus and newborn child may be challenged by mental health issues which can cause impaired functioning and poorer health outcomes. Families with complex problems need interdisciplinary interventions starting in early pregnancy to be prepared for motherhood and to ensure healthy child development. This study aims to examine the effects of an early and coordinated intervention (the Family Clinic and Municipality (FACAM) intervention) offered to vulnerable pregnant women during pregnancy and the child's first year of life on the mother-child relationship, maternal social functioning, mental health, reflective functioning, well-being, parental stress, and the development and well-being of the child. METHODS: The study is a prospective randomized controlled trial where we will randomize 320 pregnant women enrolled to receive antenatal care at the family clinic at Odense University Hospital, to either FACAM intervention or usual care. The FACAM intervention consists of extra support by a health nurse or family therapist during pregnancy and until the child starts school. The intervention is most intensive in the first 12 months and also includes attachment-based support provided either individually or in groups. The participants are assessed at baseline, and when the infant is 3 and 12 months old. The primary outcome is maternal sensitivity measured by the Coding Interactive Behavior (CIB) instrument. Secondary outcomes include prenatal parental reflective functioning, mental well-being, depressive symptoms, breastfeeding duration, maternal satisfaction, child development, parent competence, parental stress, and activities with the child. DISCUSSION: The trial is expected to contribute knowledge about the effect of early coordinated support in antenatal and postnatal care for vulnerable pregnant women and their families. TRIAL REGISTRATION: ClinicalTrials.gov NCT03659721 . Registered on September 6, 2018.

The Nereid on the rise: Platynereis as a model system.

The Nereid Platynereis dumerilii (Audouin and Milne Edwards (Annales des Sciences Naturelles 1:195-269, 1833) is a marine annelid that belongs to the Nereididae, a family of errant polychaete worms. The Nereid shows a pelago-benthic life cycle: as a general characteristic for the superphylum of Lophotrochozoa/Spiralia, it has spirally cleaving embryos developing into swimming trochophore larvae. The larvae then metamorphose into benthic worms living in self-spun tubes on macroalgae. Platynereis is used as a model for genetics, regeneration, reproduction biology, development, evolution, chronobiology, neurobiology, ecology, ecotoxicology, and most recently also for connectomics and single-cell genomics. Research on the Nereid started with studies on eye development and spiralian embryogenesis in the nineteenth and early twentieth centuries. Transitioning into the molecular era, Platynereis research focused on posterior growth and regeneration, neuroendocrinology, circadian and lunar cycles, fertilization, and oocyte maturation. Other work covered segmentation, photoreceptors and other sensory cells, nephridia, and population dynamics. Most recently, the unique advantages of the Nereid young worm for whole-body volume electron microscopy and single-cell sequencing became apparent, enabling the tracing of all neurons in its rope-ladder-like central nervous system, and the construction of multimodal cellular atlases. Here, we provide an overview of current topics and methodologies for P. dumerilii, with the aim of stimulating further interest into our unique model and expanding the active and vibrant Platynereis community.

Family Club Denmark #strongertogether - a volunteer intervention for disadvantaged families: study protocol for a quasi-experimental trial.

BACKGROUND: Need-oriented family support programs are examples of voluntary-based interventions increasingly recognized by the public sector as an important contribution to health and social care provision. Voluntary interventions are attractive because of their focus on activism, inclusion, and participation, but also their low cost and easy accessibility. There is an increasing demand for documentation of the effectiveness of family support programs. Methodologically sound studies are, however, limited and findings are generally inconsistent. This trial aims to assess the effectiveness of the volunteer-based intervention Family Club Denmark on parental stress, mental health, development and well-being of parents and children and to get insight into the experiences of both volunteers and families. METHODS: This is a prospective quasi-experimental trial with two conditions: (1) intervention group participating in Family Club Denmark and (2) wait-list control group. Participants are families with children aged 2-12 years who wish to participate in the program. Participants are allocated to intervention primarily after a first-come-first-serve principle, and further families will join the wait-list and be offered participation after around 6 months. Quantitative data are collected through web surveys at three time-points: at baseline, post-intervention (6 months after baseline), and follow-up (12 months after baseline). The primary outcome is mental health. Secondary outcomes include parenting behavior, parenting stress, self-efficacy and self-worth, family routines and child well-being. Qualitative data are collected through observations, focus groups, and interviews. DISCUSSION: This trial is among the first experimental studies of a group-based third sector need-oriented family support program offered to a wide array of families. The trial will provide important knowledge on the effectiveness of a volunteer-based family intervention on important outcomes such as mental health, self-efficacy, family routines. Furthermore, the trial will provide knowledge on volunteer, parent, and child experiences with participating in the intervention and knowledge on how to conduct experimental trails in a complex volunteer environment. TRIAL REGISTRATION: ClinicalTrials.govNCT03657888 (registered 29.08.2018).

From spiral cleavage to bilateral symmetry: the developmental cell lineage of the annelid brain.

BACKGROUND: During early development, patterns of cell division-embryonic cleavage-accompany the gradual restriction of blastomeres to specific cell fates. In Spiralia, which include annelids, mollusks, and flatworms, "spiral cleavage" produces a highly stereotypic, spiral-like arrangement of blastomeres and swimming trochophore-type larvae with rotational (spiral) symmetry. However, starting at larval stages, spiralian larvae acquire elements of bilateral symmetry, before they metamorphose into fully bilateral juveniles. How this spiral-to-bilateral transition occurs is not known and is especially puzzling for the early differentiating brain and head sensory organs, which emerge directly from the spiral cleavage pattern. Here we present the developmental cell lineage of the Platynereis larval episphere. RESULTS: Live-imaging recordings from the zygote to the mid-trochophore stage (~ 30 hpf) of the larval episphere of the marine annelid Platynereis dumerilii reveal highly stereotypical development and an invariant cell lineage of early differentiating cell types. The larval brain and head sensory organs develop from 11 pairs of bilateral founders, each giving rise to identical clones on the right and left body sides. Relating the origin of each bilateral founder pair back to the spiral cleavage pattern, we uncover highly divergent origins: while some founder pairs originate from corresponding cells in the spiralian lineage on each body side, others originate from non-corresponding cells, and yet others derive from a single cell within one quadrant. Integrating lineage and gene expression data for several embryonic and larval stages, we find that the conserved head patterning genes otx and six3 are expressed in bilateral founders representing divergent lineage histories and giving rise to early differentiating cholinergic neurons and head sensory organs, respectively. CONCLUSIONS: We present the complete developmental cell lineage of the Platynereis larval episphere, and thus the first comprehensive account of the spiral-to-bilateral transition in a developing spiralian. The bilateral symmetry of the head emerges from pairs of bilateral founders, similar to the trunk; however, the head founders are more numerous and show striking left-right asymmetries in lineage behavior that we relate to differential gene expression.

The ancestral retinoic acid receptor was a low-affinity sensor triggering neuronal differentiation.

Retinoic acid (RA) is an important intercellular signaling molecule in vertebrate development, with a well-established role in the regulation of hox genes during hindbrain patterning and in neurogenesis. However, the evolutionary origin of the RA signaling pathway remains elusive. To elucidate the evolution of the RA signaling system, we characterized RA metabolism and signaling in the marine annelid Platynereis dumerilii, a powerful model for evolution, development, and neurobiology. Binding assays and crystal structure analyses show that the annelid retinoic acid receptor (RAR) binds RA and activates transcription just as vertebrate RARs, yet with a different ligand-binding pocket and lower binding affinity, suggesting a permissive rather than instructive role of RA signaling. RAR knockdown and RA treatment of swimming annelid larvae further reveal that the RA signal is locally received in the medial neuroectoderm, where it controls neurogenesis and axon outgrowth, whereas the spatial colinear hox gene expression in the neuroectoderm remains unaffected. These findings suggest that one early role of the new RAR in bilaterian evolution was to control the spatially restricted onset of motor and interneuron differentiation in the developing ventral nerve cord and to indicate that the regulation of hox-controlled anterior-posterior patterning arose only at the base of the chordates, concomitant with a high-affinity RAR needed for the interpretation of a complex RA gradient.

Cell lineage and cell cycling analyses of the 4d micromere using live imaging in the marine annelid Platynereis dumerilii.

Cell lineage, cell cycle, and cell fate are tightly associated in developmental processes, but in vivo studies at single-cell resolution showing the intricacies of these associations are rare due to technical limitations. In this study on the marine annelid Platynereis dumerilii, we investigated the lineage of the 4d micromere, using high-resolution long-term live imaging complemented with a live-cell cycle reporter. 4d is the origin of mesodermal lineages and the germline in many spiralians. We traced lineages at single-cell resolution within 4d and demonstrate that embryonic segmental mesoderm forms via teloblastic divisions, as in clitellate annelids. We also identified the precise cellular origins of the larval mesodermal posterior growth zone. We found that differentially-fated progeny of 4d (germline, segmental mesoderm, growth zone) display significantly different cell cycling. This work has evolutionary implications, sets up the foundation for functional studies in annelid stem cells, and presents newly established techniques for live imaging marine embryos.

Light-sheet microscopy for everyone? Experience of building an OpenSPIM to study flatworm development.

BACKGROUND: Selective plane illumination microscopy (SPIM a type of light-sheet microscopy) involves focusing a thin sheet of laser light through a specimen at right angles to the objective lens. As only the thin section of the specimen at the focal plane of the lens is illuminated, out of focus light is naturally absent and toxicity due to light (phototoxicity) is greatly reduced enabling longer term live imaging. OpenSPIM is an open access platform (Pitrone et al. 2013 and OpenSPIM.org) created to give new users step-by-step instructions on building a basic configuration of a SPIM microscope, which can in principle be adapted and upgraded to each laboratory's own requirements and budget. Here we describe our own experience with the process of designing, building, configuring and using an OpenSPIM for our research into the early development of the polyclad flatworm Maritigrella crozieri - a non-model animal. RESULTS: Our OpenSPIM builds on the standard design with the addition of two colour laser illumination for simultaneous detection of two probes/molecules and dual sided illumination, which provides more even signal intensity across a specimen. Our OpenSPIM provides high resolution 3d images and time lapse recordings, and we demonstrate the use of two colour lasers and the benefits of two color dual-sided imaging. We used our microscope to study the development of the embryo of the polyclad flatworm M. crozieri. The capabilities of our microscope are demonstrated by our ability to record the stereotypical spiral cleavage pattern of M. crozieri with high-speed multi-view time lapse imaging. 3D and 4D (3D + time) reconstruction of early development from these data is possible using image registration and deconvolution tools provided as part of the open source Fiji platform. We discuss our findings on the pros and cons of a self built microscope. CONCLUSIONS: We conclude that home-built microscopes, such as an OpenSPIM, together with the available open source software, such as MicroManager and Fiji, make SPIM accessible to anyone interested in having continuous access to their own light-sheet microscope. However, building an OpenSPIM is not without challenges and an open access microscope is a worthwhile, if significant, investment of time and money. Multi-view 4D microscopy is more challenging than we had expected. We hope that our experience gained during this project will help future OpenSPIM users with similar ambitions.

Development of the annelid axochord: insights into notochord evolution.

The origin of chordates has been debated for more than a century, with one key issue being the emergence of the notochord. In vertebrates, the notochord develops by convergence and extension of the chordamesoderm, a population of midline cells of unique molecular identity. We identify a population of mesodermal cells in a developing invertebrate, the marine annelid Platynereis dumerilii, that converges and extends toward the midline and expresses a notochord-specific combination of genes. These cells differentiate into a longitudinal muscle, the axochord, that is positioned between central nervous system and axial blood vessel and secretes a strong collagenous extracellular matrix. Ancestral state reconstruction suggests that contractile mesodermal midline cells existed in bilaterian ancestors. We propose that these cells, via vacuolization and stiffening, gave rise to the chordate notochord.

Planarian regeneration: achievements and future directions after 20 years of research.

Planarians can undergo dramatic changes in body size and regenerate their entire body plan from small pieces after cutting. This remarkable morphological plasticity has made them an excellent model in which to analyze phenomena such as morphogenesis, restoration of pattern and polarity, control of tissue proportions and tissue homeostasis. They have a unique population of pluripotent stem cells in the adult that can give rise to all differentiated cell types, including the germ cells. These cellular characteristics provide an excellent opportunity to study the mechanisms involved in the maintenance and differentiation of cell populations in intact and regenerating animals. Until recently, the planarian model system lacked opportunities for genetic analysis; however, this handicap was overcome in the last decade through the development of new molecular methods which have been successfully applied to planarians. These techniques have allowed analysis of the temporal and spatial expression of genes, as well as interference with gene function, generating the first phenotypes by loss or gain of function. Finally, the sequencing of the planarian genome has provided the essential tools for an in-depth analysis of the genomic regulation of this model system. In this review, we provide an overview of planarians as a model system for research into development and regeneration and describe new lines of investigation in this area.

Stem cells and regeneration in planarians.

Understanding stem cells is a major goal of current research because of its potential medical applications. Although great advances have been made, such as the culturing and differentiation of embryonic stem cells and reprogramming of cell fates, many basic questions remain unanswered. Describing the mechanisms underlying regeneration will help to understand the biology of stem cells and therefore to control their behavior. While regeneration is being studied in a variety of models, the planarian is particularly noteworthy. In this model system a fragment as small as 1/279 of the animal can regenerate completely within a few weeks. These animals can also grow and degrow--specifically degenerating certain tissues--according to environmental conditions, thus demonstrating a complete control of their stem cell dynamics. However, one of the most interesting aspects of the planarian model system is the presence of a unique type of stem cell that can differentiate into all cell types found in the organism, including the germ line. This represents a simple, extremely powerful, and accessible stem cell system in which to address a variety of important questions. In the last ten years, molecular, cellular, and bioinformatics tools have been established for use in this model, making it ideally placed for in vivo analysis of stem cells in their natural environment without ethical complications.

The planarian nanos-like gene Smednos is expressed in germline and eye precursor cells during development and regeneration.

Planarians are highly regenerative organisms with the ability to remake all their cell types, including the germ cells. The germ cells have been suggested to arise from totipotent neoblasts through epigenetic mechanisms. Nanos is a zinc-finger protein with a widely conserved role in the maintenance of germ cell identity. In this work, we describe the expression of a planarian nanos-like gene Smednos in two kinds of precursor cells namely, primordial germ cells and eye precursor cells, during both development and regeneration of the planarian Schmidtea mediterranea. In sexual planarians, Smednos is expressed in presumptive male primordial germ cells of embryos from stage 8 of embryogenesis and throughout development of the male gonads and in the female primordial germ cells of the ovary. Thus, upon hatching, juvenile planarians do possess primordial germ cells. In the asexual strain, Smednos is expressed in presumptive male and female primordial germ cells. During regeneration, Smednos expression is maintained in the primordial germ cells, and new clusters of Smednos-positive cells appear in the regenerated tissue. Remarkably, during the final stages of development (stage 8 of embryogenesis) and during regeneration of the planarian eye, Smednos is expressed in cells surrounding the differentiating eye cells, possibly corresponding to eye precursor cells. Our results suggest that similar genetic mechanisms might be used to control the differentiation of precursor cells during development and regeneration in planarians.