Biogenic reefs as structuring factor in <i>Pleuronectes platessa</i> (Plaice) nursery

The structural distribution of juvenile flatfish in nursery areas is generally studied on a larger scale on which the effects of abiotic factors such as sediment characteristics, beach profile, tides, and turbidity dominate. The biotic structuring factor has never before been investigated from a very small scale-perspective. The latter is the subject of the present study. In an in situ experimental sampling design, the structuring effect of biogenic reefs on the distribution of Pleuronectes platessa (Plaice) in an intertidal nursery area is investigated. The density distribution of this flatfish species is significantly (p Lanice conchilega. The importance of this reef builder has been highlighted before in other studies but present study demonstrates that not only the benthic biodiversity is affected by L. conchilega reefs, but that the distribution pattern of P. platessa is structured by them as well. This structuring impact of small-scale benthic reefs creating a patchy environment in nursery areas potentially plays an important role in other marine environments and indicates the need for further research on the ecological function of benthic reef environments for several flatfish species. Further modification of these biogenic habitats may lead to a loss of one or more ecosystem functions which flatfish species depend on

Importance of eco-engineered inshore habitats for juvenile flatfish

Within coastal nurseries, the distribution of juvenile flatfish may depend on small-scale habitat variability. The present study investigates the relation between the distribution of two juvenile flatfish species (Pleuronectes platessa and Limanda limanda) with two sessile tube dwelling polychaetes that create specific habitats at high densities. Their modulating effects make them classify as ecosystem engineers. Lanice conchilega and Owenia fusiformis, both frequently occurring in the coastal zones of the North Sea are the studied ecosystem engineers. These two benthic tube worm systems are investigated for their function as ‘essential juvenile habitat’ (EJH) in two geographical areas (the Belgian part of North Sea and the Dutch part of the Wadden Sea). General responses were identified by comparing relative differences between ecosystem engineered habitats and adjacent bare sand (i.e. non ecosystem engineered) habitats. Results show that both flatfish species select for the ecosystem engineered habitat. This behaviour was further investigated using stomach content analyses. For P. platessa occurring in L. conchilega habitat, this selection was explained as feeding behaviour. For the habitats created by O. fusiformis, no such a relation was found. For L. limanda higher densities within the ecosystem engineered habitats cannot be explained by feeding advantage but by the use of this habitat as a shelter. Therefore, higher flatfish densities could be explained by an antipredation behaviour. Lanice conchilega aggregations may be more important as feeding area for juvenile flatfish species in comparison with O. fusiformis aggregations. The indirect impacts of bottom trawling on benthic tube worm aggregations by reducing the suitability of the areas for juvenile flatfishes are discussed. We conclude that the emergent structures in the flatfish nursery area play an important role in the ecology of the juvenile flatfishes as feeding ground and/or as refuge from predation. These small-scale aspects of nursery grounds can be considered as EJH and merit attention in habitat suitability models as well as in marine conservation

Expanding the clinical spectrum of biglycan-related Meester-Loeys syndrome

\ua9 The Author(s) 2024.Pathogenic loss-of-function variants in BGN, an X-linked gene encoding biglycan, are associated with Meester-Loeys syndrome (MRLS), a thoracic aortic aneurysm/dissection syndrome. Since the initial publication of five probands in 2017, we have considerably expanded our MRLS cohort to a total of 18 probands (16 males and 2 females). Segregation analyses identified 36 additional BGN variant-harboring family members (9 males and 27 females). The identified BGN variants were shown to lead to loss-of-function by cDNA and Western Blot analyses of skin fibroblasts or were strongly predicted to lead to loss-of-function based on the nature of the variant. No (likely) pathogenic missense variants without additional (predicted) splice effects were identified. Interestingly, a male proband with a deletion spanning the coding sequence of BGN and the 5’ untranslated region of the downstream gene (ATP2B3) presented with a more severe skeletal phenotype. This may possibly be explained by expressional activation of the downstream ATPase ATP2B3 (normally repressed in skin fibroblasts) driven by the remnant BGN promotor. This study highlights that aneurysms and dissections in MRLS extend beyond the thoracic aorta, affecting the entire arterial tree, and cardiovascular symptoms may coincide with non-specific connective tissue features. Furthermore, the clinical presentation is more severe and penetrant in males compared to females. Extensive analysis at RNA, cDNA, and/or protein level is recommended to prove a loss-of-function effect before determining the pathogenicity of identified BGN missense and non-canonical splice variants. In conclusion, distinct mechanisms may underlie the wide phenotypic spectrum of MRLS patients carrying loss-of-function variants in BGN

Video transects reveal that tidal sand waves affect the spatial distribution of benthic organisms and sand ripples

The sandy seabed of shallow coastal shelf seas displays morphological patterns of various dimensions. The seabed also harbors a rich ecosystem. Increasing pressure from human-induced disturbances necessitates further study on drivers of benthic community distributions over morphological patterns. Moreover, a greater understanding of the sand ripple distribution over tidal sand waves may improve morphological model predictions. Here we analyzed the biotic abundance and ripple morphology in sand wave troughs and crests using video transects. We found that both the epibenthos and endobenthos are significantly more abundant in sand wave troughs, where ripples are less abundant and more irregularly shaped. Finally, we show that camera systems are relatively quick and effective tools to study biotic spatial patterns in relation to seabed morphology

IPSC reprogramming of two patients with spondyloepimetaphyseal dysplasia (SEMD, biglycan type).

Hemizygous missense variants in the X-linked BGN gene, encoding the extracellular matrix protein biglycan, cause spondyloepimetaphyseal dysplasia (SEMD, biglycan type), which is clinically characterized by short stature, brachydactyly and osteoarthritis. Little is known about the pathomechanisms underlying SEMD, biglycan type. IPSC-derived chondrocyte disease models have been shown to exhibit several key aspects of known disease mechanisms of skeletal dysplasias and are therefore considered highly suitable human disease models to study SEMD, biglycan type. Prior to creating iPSC-chondrocytes, dermal fibroblasts of two male patients with SEMD, biglycan type, carrying the p.Gly259Val variant were successfully reprogrammed into iPSCs using the CytoTune(TM)-iPS 2.0 Sendai Kit (Invitrogen)

The role of structuring benthos for juvenile flatfish

Within coastal nurseries, the distribution of juvenile flatfish may depend on small-scale habitat variability. The presence of ecosystem engineers is known to have important impacts in coastal sediments. Lanice conchilega is a well-known marine ecosystem engineer of shallow soft bottom ecosystems, shaping the macrobenthic community and attracting flatfish. The present study examines the relation between juvenile flatfish and L conchilega reefs through two experiments. In a field experiment in the Dutch part of the North Sea, the benthic habitat is evaluated by comparing relative differences in numbers of juvenile flatfish between ecosystem engineered habitats and adjacent bare sand (i.e. non-ecosystem engineered) habitats. The hypothetical shelter seeking behaviour was further examined using stomach content analyses. Results show that juvenile plaice Pleuronectes platessa was the dominant species within the tube worm habitat and the species selects specifically for this biogenic habitat. This selection was explained as feeding behaviour. In a complementary laboratory study, food was excluded and the shelter function of the ecosystem engineered habitat was investigated. This experiment quantifies the selection for this habitat by juveniles of the common sole Solea solea. Results from the flume experiment, manipulating the number of tube worms, show that distribution of sole was not random when current velocities are high. The selected habitat is the one with low density tube worm aggregations. Overall, we conclude that structuring benthos plays an important role for juvenile flatfish, both as refuge and as feeding ground