Lateral Plate Research Articles

Abstract 4134622: Hyperglycemia Induces Heterotaxy Syndrome by Lowering Intracellular pH

Background: Pregestational diabetes is an established risk factor for congenital heart disease (CHD), including heterotaxy syndrome, which results from abnormal left-right (L-R) axis. However, the specific mechanism by which hyperglycemia disturbs the L-R axis still remains unsolved. In addition, it is unknown how a variety of heterotaxy is provoked by pregestational diabetes. Methods: We conducted whole-mount in situ hybridization, reporter analysis and RNA-seq in mouse embryos of streptozotocin-induced diabetic dams and Wnt3a –/– embryos. Additionally, the effect of high-glucose conditions on intracellular pH (pH i ) was investigated. We also examined the influence of maternal vitamin A intake on L-R axis formation in embryos of diabetic dams. Results: We observed various patterns of Pitx2 expression in embryos of diabetic dams, indicating disrupted L-R axis. The initial step of L-R axis formation was impaired, with Nodal expression, which induces Nodal - Pitx2 cascade in the lateral plate mesoderm, being regressed in the node. Consistent with the resemblance to the phenotype of Wnt3a –/– embryos, canonical Wnt signaling was downregulated in embryos of diabetic dams. As the RNA-seq analysis suggested dysregulation of glycolysis, we assessed pH i to find that hyperglycemia lowers pH i in the primitive streak, leading to the regression of Nodal expression in the node. Furthermore, maternal vitamin A intake was found to increase the incidence and diversity of L-R axis defects, likely as a result of dysregulation of retinoic acid metabolism apparent in embryos of diabetic dams and Wnt3a –/– embryos. Conclusions: Hyperglycemia downregulates canonical Wnt signaling by lowering pH i , which not only impairs L-R axis formation but also dysregulates retinoid metabolism. Consequently, embryos of diabetic dams become vulnerable to fluctuation of maternal vitamin A intake, resulting in diverse L-R axis defects. These findings provide insights into the etiology of CHD and suggest the importance of diet for prevention of heterotaxy during diabetic pregnancy.

Design and validation of finite element models for the assessment of post-fixation distal femur fracture motion.

Fracture site motion is thought to play an important role in the healing of complex fractures of the distal femur via mechanotransduction. Measuring this motion in vivo is challenging, and this has led researchers to turn to finite element modeling approaches to gain insights into the mechanical environment at the fracture site. Developing a systematic understanding of the effect of different model choices for distal femur fractures may allow more accurate prediction of fracture site motion from these types of simulations. In this study, we aim to assess the effect of four different modeling choices and parameters. We looked at the effect of using bone specific density distributions vs generic values, employing landmark-based geometry generation, varying fracture alignment within clinically relevant ranges, and determining whether direct apposition of the fracture to the plate was achieved. For validation, five cadaveric femurs had fractures created and repaired with plated constructs, and these were then loaded and fracture site motion was directly measured. We found that using landmark based bone geometry and patient-specific bone density distributions had a minimal effect on the overall model predictions. Changing the alignment, particularly into varus and procurvatum could have a large (>50%) effect on predicted shear motion, as could direct apposition of the bone to the plate. These findings demonstrate that modeling choices can play an important role in simulating distal femur fracture mechanics, and it is particularly critical that patient customized models attempt to accurately represent alignment of the bone fragments and lateral plate apposition.

Modeling of Skeletal Development and Diseases Using Human Pluripotent Stem Cells.

Human skeletal elements are formed from distinct origins at distinct positions of the embryo. For example, the neural crest produces the facial bones, the paraxial mesoderm produces the axial skeleton, and the lateral plate mesoderm produces the appendicular skeleton. During skeletal development, different combinations of signaling pathways are coordinated from distinct origins during the sequential developmental stages. Models for human skeletal development have been established using human pluripotent stem cells (hPSCs) and by exploiting our understanding of skeletal development. Stepwise protocols for generating skeletal cells from different origins have been designed to mimic developmental trails. Recently, organoid methods have allowed the multicellular organization of skeletal cell types to recapitulate complicated skeletal development and metabolism. Similarly, several genetic diseases of the skeleton have been modeled using patient-derived induced pluripotent stem cells and genome-editing technologies. Model-based drug screening is a powerful tool for identifying drug candidates. This review briefly summarizes our current understanding of the embryonic development of skeletal tissues and introduces the current state-of-the-art hPSC methods for recapitulating skeletal development, metabolism, and diseases. We also discuss the current limitations and future perspectives for applications of the hPSC-based modeling system in precision medicine in this research field.

Hyperglycaemia induces diet-dependent defects of the left-right axis by lowering intracellular pH

Pregestational diabetes is a risk factor for congenital anomalies, including heterotaxy syndrome, a rare birth defect characterized by the abnormal arrangement of organs relative to the left-right (L-R) body axis. To provide insight into the underlying mechanism by which diabetes induces heterotaxy, we here analyzed the L-R axis of mouse embryos of diabetic dams. Various Pitx2 expression patterns indicative of disruption of L-R axis formation were apparent in such embryos. Expression of Nodal at the node, which triggers a Nodal-Pitx2 expression cascade in lateral plate mesoderm, showed marked regression associated with L-R axis malformation. This regression was similar to that apparent in Wnt3a−/− embryos, and canonical Wnt signalling was indeed found to be downregulated in embryos of diabetic dams. RNA sequencing revealed dysregulation of glycolysis in embryos of diabetic dams, and high glucose lowered intracellular pH in the primitive streak, leading to the suppression of Wnt signalling and the regression of Nodal expression. Of note, maternal vitamin A intake increased the incidence of L-R axis defects in embryos of diabetic dams, with dysregulation of retinoic acid metabolism being apparent in these embryos and in Wnt3a−/− embryos. Our results shed light on the mechanisms underlying embryopathies associated with maternal diabetes and suggest the importance of diet for prevention of heterotaxy.

An Unusual Skin Finding in a Rare Case of Goltz Syndrome

Abstract Introduction/Objective Goltz Syndrome (Focal Dermal Hypoplasia) is a rare X linked dominant genetic disorder with various dermatologic, musculoskeletal and neurologic manifestations, secondary to a mutation in the PORCN gene. Skin findings include telangiectasias, raspberry-like papillomas (angiofibroma like lesions), nodular fat herniation, xerosis and photosensitivity. Lesions are bilateral, and asymmetrically distribututed along the lines of Blasco. The adipocytic lesions can be diagnosed via a skin biopsy showing adipose tissue in the superficial epidermis and dermis or via molecular techniques showing a mutation in the PORCN gene. Here we report a case of Goltz Syndrome with unique dermal findings. Methods/Case Report A male infant presented at birth with mild diffuse xerosis, large hypopigmented and depigmented atrophic patches and plaques and multiple pink yellow red exophyitic soft papules distributed asymetrically across the body along the lines of Blascho. Additionally the patient had clinodactly, widely spaced nipples, extra pads of fat in the toes and philtrum and fingernails with longitudal ridges and lateral nail plate deviation. A diagnosis of Goltz syndrome was made via molecular analysis that showed mosiacism at C.502G>A (p.Gly168Arg) in the PORCN gene. The patient had a very superficial 2-3 mm erosion at the intersection between the scrotum and perineum. At 18 months, this had grown to finger like projections and eventually grew into multiple tan red exophytic warty papillomatous telangactatic like lesions measuring 3.0 x 0.8 cm that were painful and bled easily. A biopsy of this lesion showed focal mild epidermal hyperplasia and elongation of the rete ridges with wide spread diffuse vascular proliferation with multiple ectactic vessels along with mild dermal and perivascular inflammatory infiltrates. Also noted was infiltration of mature adipose tissue in the superficial epidermis and dermis. We preformed elastin and trichrome stains to identify if this lesion was reactive in nature or de novo. Our results showed retained elastin staining with a negative trichrome eluding to a denovo process. Additionally GLUT1 was negative, ruling out an infantile hemangioma. The above findings in this lesion do not represent any previously described dermatologic entity. Results (if a Case Study enter NA) NA Conclusion This is a rare and unique dermatologic finding of a case of Goltz sydrome, which itself is a rare disorder. In our literature review, this is the only case of Goltz Syndrome thusfar to have presented with this unique skin lesion.

Cranial anatomy of Bagualia alba (Dinosauria, Eusauropoda) from the Early Jurassic of Patagonia and the implications for sauropod cranial evolution

Sauropods are the largest terrestrial vertebrates ever known. During their evolution, they underwent numerous morphological changes, some of which occurred at the end of the Early Jurassic. However, current knowledge of Early Jurassic dinosaurs is scarce, especially cranial information. Here we describe the skull of the basal eusauropod Bagualia alba from the Cañadón Asfalto Formation (Toarcian; Early Jurassic) of Patagonia, Argentina, which represents the most complete eusauropod skull from the late Early Jurassic worldwide. The osteological description and phylogenetic relationships of Bagualia allowed us to determine the acquisition of the common cranial bauplan of eusauropods at the end of the Early Jurassic: a tall and robust rostrum with great retraction of the external nares; a deep narial fossa; a reduced antorbital fenestra; verticalization of the lacrimal; prefrontal without an anterior process; anteroposterior shortening of the frontal; a supratemporal fenestra visible laterally; a robust braincase; ‘U’-shaped jaws in dorsal view; reduction in the number of teeth in the dentary; teeth with crown to crown occlusion; development of lateral plates in the premaxilla and maxilla; and a dorsoventral expansion of the dentary symphysis. These cranial characteristics were recently suggested to be related to a change in the diet of the sauropods toward mainly hard vegetation. In this context, Bagualia contributes to filling a gap in cranial evolution between the gracile skulls of Sauropodiformes and the highly robust skulls widely represented in Middle Jurassic taxa.

Modified pendulum osteotomy to correct severe tibial varus deformity

Correction of asevere tibial varus deformity near the knee joint with only aslight influence on leg length and patella height. Medial osteoarthritis and/or cartilage damage with asevere varus deformity > 10° with amedial proximal tibial angle (MPTA) < 80°. Femoral varus deformity with lateral distal femoral angle > 91°, severe lateral cartilage damage, lateral osteoarthritis, lateral meniscus loss. Skin incision of approx. 8-10 cm between the tibial tuberosity and the head of the fibula. Exploration of the peroneal nerve. Detachment of the extensors. Insertion of an obliquely ascending guidewire ending approximately 10 mm below the medial articular surface. Insertion of asecond guidewire. This aims at the middle of the first wire (hemi wedge). Check the wire position under fluoroscopy. Osteotomy with an oscillating saw under cooling. Removal of the wedge and closure of the osteotomy. Percutaneous needling of the medial collateral ligament with acannula to carefully lengthen the ligament. Check the correction result with ametal rod. Osteosynthesis with lateral angle-stable plate. Partial weight-bearing with 10 kg for 6weeks postoperatively, free range of motion. Reports from the literature show that good clinical results can be achieved with this procedure for severe tibial varus deformities. Postoperative leg length discrepancies are less common with this procedure than with laterally closing osteotomy.

The pericardium forms as a distinct structure during heart formation.

The heart integrates diverse cell lineages into a functional unit, including the pericardium, a mesothelial sac that supports heart movement, homeostasis, and immune responses. However, despite its critical roles, the developmental origins of the pericardium remain uncertain due to disparate models. Here, using live imaging, lineage tracking, and single-cell transcriptomics in zebrafish, we find the pericardium forms within the lateral plate mesoderm from dedicated anterior mesothelial progenitors and distinct from the classic heart field. Imaging of transgenic reporters in zebrafish documents lateral plate mesoderm cells that emerge lateral of the classic heart field and among a continuous mesothelial progenitor field. Single-cell transcriptomics and trajectories of hand2-expressing lateral plate mesoderm reveal distinct populations of mesothelial and cardiac precursors, including pericardial precursors that are distinct from the cardiomyocyte lineage. The mesothelial gene expression signature is conserved in mammals and carries over to post-natal development. Light sheet-based live-imaging and machine learning-supported cell tracking documents that during heart tube formation, pericardial precursors that reside at the anterior edge of the heart field migrate anteriorly and medially before fusing, enclosing the embryonic heart to form a single pericardial cavity. Pericardium formation proceeds even upon genetic disruption of heart tube formation, uncoupling the two structures. Canonical Wnt/β-catenin signaling modulates pericardial cell number, resulting in a stretched pericardial epithelium with reduced cell number upon canonical Wnt inhibition. We connect the pathological expression of secreted Wnt antagonists of the SFRP family found in pediatric dilated cardiomyopathy to increased pericardial stiffness: sFRP1 in the presence of increased catecholamines causes cardiomyocyte stiffness in neonatal rats as measured by atomic force microscopy. Altogether, our data integrate pericardium formation as an independent process into heart morphogenesis and connect disrupted pericardial tissue properties such as pericardial stiffness to pediatric cardiomyopathies.

Immobilization secondary to cell death of muscle precursors with a dual transcriptional signature contributes to the emu wing skeletal pattern

Limb reduction has occurred multiple times in tetrapod history. Among ratites, wing reductions range from mild vestigialization to complete loss, with emus (Dromaius novaehollandiae) serving as a model for studying the genetic mechanisms behind limb reduction. Here, we explore the developmental mechanisms underlying wing reduction in emu. Our analyses reveal that immobilization resulting from the absence of distal muscles contributes to skeletal shortening, fusion and left-right intraindividual variation. Expression analysis and single cell-RNA sequencing identify muscle progenitors displaying a dual lateral plate mesodermal and myogenic signature. These cells aggregate at the proximal region of wing buds and undergo cell death. We propose that this cell death, linked to the lack of distal muscle masses, underlines the morphological features and variability in skeletal elements due to reduced mechanical loading. Our results demonstrate that differential mobility during embryonic development may drive morphological diversification in vestigial structures.

The combined internal and external fixation surgery is effective and safe in treating posterior lateral tibial plateau fractures: An observational study.

To investigate the treatment outcomes of combined internal and external fixation surgery for patients with posterior lateral tibial plateau fractures and explore its safety. The study was conducted from February 2020 to February 2023 and included a total of 77 patients with Schatzker IV and Schatzker V type posterior lateral tibial plateau fractures. Patients were divided into control group and treatment group according to different treatment methods: the control group with 38 cases received treatment with dual-support plates, and the study group with 39 cases received treatment with internal fixation using medial plates combined with lateral locking plates. Clinical indicators during treatment, immediate postoperative and 12-month postoperative radiographic indicators, Rasmussen knee joint function scores before and 3 months after surgery, knee joint function recovery, quality of life, and postoperative complications were recorded and compared between the 2 groups. The inter-group comparisons were made for intraoperative blood loss, surgical duration, and the time to start weight-bearing postoperatively (P > .05). The study group had shorter postoperative hospital stays and fracture healing times compared to the control group (P < .05). Immediately postoperatively, the medial tilt angle and posterior tilt angle in both groups were compared (P > .05). At 12 months postoperatively, the medial tilt angle decreased and the posterior tilt angle increased in both groups compared to immediately postoperative values (P < .05), with no significant difference between the groups (P > .05). However, at 3 months postoperatively, the scores for various dimensions in both groups increased compared to preoperative values, and the study group had higher scores than the control group (P < .05). However, at 3 months postoperatively, the quality of life scores were higher than preoperative values in both groups, with the study group having higher scores (P < .05). The occurrence of complications during the treatment period was compared between the 2 groups (P > .05). The medial and lateral combined plate fixation has a good clinical effect in the treatment of posterolateral tibial plateau fractures, which can shorten the fracture healing time, help the recovery of knee joint function and improve the quality of life of patients after operation, and has high safety in the treatment process.

Drivers of vessel progenitor fate define intermediate mesoderm dimensions by inhibiting kidney progenitor specification

Proper organ formation depends on the precise delineation of organ territories containing defined numbers of progenitor cells. Kidney progenitors reside in bilateral stripes of posterior mesoderm that are referred to as the intermediate mesoderm (IM). Previously, we showed that the transcription factors Hand2 and Osr1 act to strike a balance between the specification of the kidney progenitors in the IM and the vessel progenitors in the laterally adjacent territory. Recently, the transcription factor Npas4l – an early and essential driver of vessel and blood progenitor formation – was shown to inhibit kidney development. Here we demonstrate how kidney progenitor specification is coordinated by hand2, osr1, and npas4l. We find that npas4l and the IM marker pax2a are transiently co-expressed in the posterior lateral mesoderm, and npas4l is necessary to inhibit IM formation. Consistent with the expression of npas4l flanking the medial and lateral sides of the IM, our findings suggest roles for npas4l in defining the IM boundaries at each of these borders. At the lateral IM border, hand2 promotes and osr1 inhibits the formation of npas4l-expressing lateral vessel progenitors, and hand2 requires npas4l to inhibit IM formation and to promote vessel formation. Meanwhile, npas4l appears to have an additional role in suppressing IM fate at the medial border: npas4l loss-of-function enhances hand2 mutant IM defects and results in excess IM generated outside of the lateral hand2-expressing territory. Together, our findings reveal that establishment of the medial and lateral boundaries of the IM requires inhibition of kidney progenitor specification by the neighboring drivers of vessel progenitor fate.

Embryonic Thyroid Hormone Insufficiency Causes Structural Anomalies in the Embryo of Domestic Chick, Gallus domesticus.

Thyroid hormone (TH) is essential for growth and development, yet its specific role during embryogenesis remains incompletely understood. This study investigates the impact of TH deficiency, induced by thiourea, a known inhibitor of thyroid peroxidase (TPO), on the development of domestic chicks. Thiourea was administered before thyroid gland formation, and its presence in treated embryos was confirmed through liquid chromatography-mass spectrometry. In silico docking revealed a strong interaction between thiourea and the CCP-like domain of TPO, which was corroborated by TPO activity assays showing reduced enzyme function. This reduction in enzyme activity led to lower embryonic TH levels and increased thyroid-stimulating hormone (TSH) secretion. Morphological analysis of newly hatched chicks revealed significant structural anomalies, particularly in lateral plate mesoderm-derived structures, including omphalocele, limb deformities, anophthalmia and craniofacial defects. Alcian blue and Alizarin red staining demonstrated reduced ossification in ribs and forelimbs, while histological analysis showed incomplete abdominal wall closure and abnormal vertebral column development. Haematological profiling of TH-deficient newly hatched chicks revealed significantly lower blood cell counts, highlighting TH's critical role in haematopoiesis. These findings emphasise the multifaceted role of TH in embryonic development, with potential implications for understanding congenital hypothyroidism and its developmental impacts, especially in regions with limited healthcare access.

Hypoxia-sonic hedgehog axis as a driver of primitive hematopoiesis development and evolution in cavefish

The teleost Astyanax mexicanus consists of surface dwelling (surface fish) and cave dwelling (cavefish) forms. Cavefish have evolved in subterranean habitats characterized by reduced oxygen levels (hypoxia) and exhibit a subset of phenotypic traits controlled by increased Sonic hedgehog (Shh) signaling along the embryonic midline. The enhancement of primitive hematopoietic domains, which are formed bilaterally in the anterior and posterior lateral plate mesoderm, are responsible for the development of more larval erythrocytes in cavefish relative to surface fish. In this study, we determine the role of hypoxia and Shh signaling in the development and evolution of primitive hematopoiesis in cavefish. We show that hypoxia treatment during embryogenesis increases primitive hematopoiesis and erythrocyte development in surface fish. We also demonstrate that upregulation of Shh midline signaling by the Smoothened agonist SAG increases primitive hematopoiesis and erythrocyte development in surface fish, whereas Shh downregulation via treatment with the Smoothened inhibitor cyclopamine decreases these traits in cavefish. Together these results suggest that hematopoietic enhancement is regulated by hypoxia and Shh signaling. Lastly, we demonstrate that hypoxia enhances expression of Shh signaling along the midline of surface fish embryos. We conclude that hypoxia-mediated Shh plasticity may be a driving force for the adaptive evolution of primitive hematopoiesis and erythrocyte development in cavefish.

A new weigeltaspid (Heterostraci) from the Early Devonian of Nunavut, Canadian Arctic, Canada, with comments on the relationships of the weigeltaspids

ABSTRACT A new weigeltaspid heterostracan, Orthogoniaspis amnicus nov. sp. represents the first weigeltaspid reported from the Early Devonian Peel Sound and Snowblind Bay formations, Nunavut, Canadian Arctic. One partially articulated specimen shows for the first time that while the main plates of the dorsal shield abutted each other the orbital, pineal and rostral plates were separated by bands of tesserae. The similarity of this arrangement to that of the corvaspids, particularly the presence of dorsal lateral plates and bands of tesserae separating the anterior plates suggests a sister-group relationship, as no other heterostracans share this arrangement. Arctic weigeltaspids range from the late Ludlow to the late Lochkovian (O. amnicus nov. sp.), which is earlier than the related European taxa suggesting an Arctic centre of development for the weigeltaspids, as has been suggested for other heterostracan taxa.

Three-dimensional culture in a bioengineered matrix and somatic cell complementation to improve growth and survival of bovine preantral follicles.

Here we explored poly(ethylene glycol) (PEG) bioengineered hydrogels for bovine preantral follicle culture with or without ovarian cell co-culture and examined the potential for differentiation of bovine embryonic stem cells (bESCs) towards gonadal somatic cells to develop a system more similar to the ovarian microenvironment. Bovine preantral follicles were first cultured in two-dimensional (2D) control or within PEG hydrogels (3D) and then co-cultured within PEG hydrogels with bovine ovarian cells (BOCs) to determine growth and viability. Finally, we tested conditions to drive differentiation of bESCs towards the intermediate mesoderm and bipotential gonad fate. Primary follicles grew over the 10-day culture period in PEG hydrogels compared to 2D control. Early secondary follicles maintained a similar diameter within the PEG while control follicles decreased in size. Follicles lost viability after co-encapsulation with BOCs; BOCs lost stromal cell signature over the culture period within hydrogels. Induction of bESCs towards gonadal somatic fate under WNT signaling was sufficient to upregulate intermediate mesoderm ( LHX1 ) and early coelomic epithelium/bipotential gonad markers ( OSR1 , GATA4 , WT1 ). Higher BMP4 concentrations upregulated the lateral plate mesoderm marker FOXF1 . PAX3 expression was not induced, indicating absence of the paraxial mesoderm lineage. Culture of primary stage preantral follicles in PEG hydrogels promoted growth compared to controls; BOCs did not maintain identity in the PEG hydrogels. Collectively, we demonstrate that PEG hydrogels can be a potential culture system for early preantral follicles pending refinements, which could include addition of ESC-derived ovarian somatic cells using the protocol described here. We demonstrate that three-dimensional bioengineered hydrogels could aid in the survival and growth of small bovine preantral follicles. Moreover, bovine embryonic stem cells have the potential to differentiate towards precursors of somatic gonadal cell types, presenting an alternative cell source for preantral follicle co-culture.

Anatomical variations of the lateral pterygoid plate and their implications for temporomandibular disorders: A CBCT study

ObjectiveTMD is a multifaceted condition with various contributing factors, but the actual impact of the lateral pterygoid plate on the development of TMD remains uncertain. This research aims to investigate the relationship between anatomical variations of the lateral pterygoid plate (LPP), including its angle and proximity to the condyle, and the prevalence of temporomandibular disorders (TMD), to improve diagnostic accuracy and therapeutic approaches for TMD. Materials & MethodsA retrospective analysis was conducted on 189 Cone Beam Computed Tomography (CBCT) images of individuals aged 18 to 45. Inclusion criteria were based on definitive diagnoses of degenerative joint disease, excluding individuals with orthodontic treatments, injuries, or craniofacial disorders.Participants were divided into TMD and control groups using standardized DC/TMD protocols for assessment. A radiologist, blinded to the patient's clinical status, then analyzed the CBCT images. LPP dimensions, angles, and condyle distances were measured using OnDemand 3D Imaging Software. ResultsThe study found a statistically significant higher average LPP length in females compared to males (right LPP p < 0,001, left LPP p = 0,004), with no significant differences in LPP-condyle distances and angles between genders. Comparing the TMD and control groups revealed a positive correlation between lateral plate angles and TMJ disorders (p = 0,044), suggesting a potential biomechanical linkage. ConclusionConclusively, the study challenges the assumption that LPP anatomical variations significantly impact TMD while underscoring a potential link between LPP angle and TMD. The novel insight into the potential role of the LPP angle in TMD provides a new direction for research and clinical practice, emphasizing the importance of considering subtle anatomical differences in the management of TMD.

Heterogeneous genomic architecture of skeletal armour traits in sticklebacks.

Whether populations adapt to similar selection pressures using the same underlying genetic variants depends on population history and the distribution of standing genetic variation at the metapopulation level. Studies of sticklebacks provide a case in point: when colonising and adapting to freshwater habitats, three-spined sticklebacks (Gasterosteus aculeatus) with high gene flow tend to fix the same adaptive alleles in the same major loci, whereas nine-spined sticklebacks (Pungitius pungitius) with limited gene flow tend to utilize a more heterogeneous set of loci. In accordance with this, we report results of quantitative trait locus (QTL) analyses using a backcross design showing that lateral plate number variation in the western European nine-spined sticklebacks mapped to three moderate-effect QTL, contrary to the major-effect QTL in three-spined sticklebacks and different from the four QTL previously identified in the eastern European nine-spined sticklebacks. Furthermore, several QTL were identified associated with variation in lateral plate size, and three moderate-effect QTL with body size. Together, these findings indicate more heterogenous and polygenic genetic underpinnings of skeletal armour variation in nine-spined than three-spined sticklebacks, indicating limited genetic parallelism underlying armour trait evolution in the family Gasterostidae.

The genetic basis of divergent melanic pigmentation in benthic and limnetic threespine stickleback

Pigmentation is an excellent trait to examine patterns of evolutionary change because it is often under natural selection. Benthic and limnetic threespine stickleback (Gasterosteus aculeatus) exhibit distinct pigmentation phenotypes, likely an adaptation to occupation of divergent niches. The genetic architecture of pigmentation in vertebrates appears to be complex. Prior QTL mapping of threespine stickleback pigmentation phenotypes has identified several candidate loci. However—relative to other morphological phenotypes (e.g., spines or lateral plates)—the genetic architecture of threespine stickleback pigmentation remains understudied. Here, we performed QTL mapping for two melanic pigmentation traits (melanophore density and lateral barring) using benthic-limnetic F2 crosses. The two traits mapped to different chromosomes, suggesting a distinct genetic basis. The resulting QTLs were additive, but explained a relatively small fraction of the total variance (~6%). QTLs maps differed by F1 family, suggesting variation in genetic architecture or ability to detect loci of small effect. Functional analysis identified enriched pathways for candidate loci. Several of the resulting candidate loci for pigmentation, including three loci in enriched pathways (bco1, sulf1, and tyms) have been previously indicated to affect pigmentation in other vertebrates. These findings add to a growing body of evidence suggesting pigmentation is often polygenic.

Morphology and feeding biology of larvae of the South African endemic water beetle genus Prosthetops Waterhouse, 1879 (Coleoptera: Hydraenidae)

The larvae of three species of the South African endemic water beetle genus Prosthetops Waterhouse, 1879 are described and illustrated for the first time. The second and third instar larvae of Prosthetops nitens (Péringuey, 1892), as well as third instar larva of P. megacephalus (Boheman, 1851) and P. wolfbergensis Bilton, 2013, are treated here. These three species share a combination of morphological and chaetotaxic characters that can be used for positive identification of larvae of this genus: head capsule with pores FC1 present, second antennomeres with two well-developed distal sensory appendages, maxillary seta Cdo1 very reduced, thoracic subprimary setae Dd’ absent, subprimary setae Dc’ minute and inserted on the boundary between pretergal and tergal areas, urogomphi moderately separated at the base, anal lobe with well-developed dorsal, lateral and ventral plates, and a lack of anal hooks. Some insights on the gut-contents of the larva of P. wolfbergensis are offered and an unusual urogomphal malformation observed in a larva of P. nitens is also described and illustrated. These are the first described larvae of the subfamily Prosthetopinae, and their morphology is compared to that of other known hydraenid larvae.

Is the Mesoarchean Mulgandinnah shear zone, Pilbara Craton, the world's oldest arc-slicing transform fault?

Abstract Arc-slicing transform faults represent an integral component of convergent margin tectonics. They are developed above oblique subduction systems, cutting through and displacing the entire magmatic section of arcs, leading to tectonic repetition of segments of the overriding plate in the ensuing orogenic collage. Extant examples clearly show this process in Sumatra, New Zealand, and the Philippines, while ancient examples are reported from the Paleozoic Altaids and Neoarchean Superior and Yilgarn cratons. Here, we report data that document that the Paleo-Mesoarchean Eastern Pilbara craton, recently interpreted to be a preserved mid-upper crustal level of a magmatic arc, is cut and repeated by a major 3.0–2.93 Ga arc-slicing fault, the Mulgandinnah, which sliced a previously 600 × 100 km segment of a Mesoarchean arc system, laterally moving different segments to their presently juxtaposed 200 × 200 km preserved fragment. This evidence demonstrates lateral plate motions by 3.0 Ga and shows oblique subduction, arc plutonism, arc-slicing, and repetition, reflecting that crustal growth in modern-style convergent margins was in full operation by the Mesoarchean.