Limb Development Research Articles

Venlafaxine induces Teratogenesis and alters SHH Gene Expression and Protein Biochemistry of Developing Gallus sp. Embryos

The use of antidepressant drugs during pregnancy is increasing globally. SNRIs and SSRIs are most widely used for treating panic disorders. Venlafaxine is an antidepressant that inhibits serotonin and norepinephrine reuptake. Given the increasing prevalence of antidepressant use during pregnancy, Venlafaxine exposure during the early stages of development could lead to changes in protein dynamics and disrupt essential gene pathways, raising concerns about the potential teratogenic effects of antidepressant exposure during pregnancy. This study explores the developmental impact of Venlafaxine, a commonly prescribed serotonin-norepinephrine reuptake inhibitor (SNRI), on protein biochemistry and gene expression in the developing Gallus gallus domesticus embryos. Significant changes in protein profiles were observed among control and Venlafaxine-treated groups. Sonic Hedgehog (SHH) gene, a key regulator of embryonic patterning and organogenesis, specifically neural tube formation, and limb development, is known for its crucial role in embryonic development. qRT-PCR analysis of Venlafaxine-treated embryos showed changes in SHH gene expression suggesting that Venlafaxine may target SHH gene expression, and potentially alter signalling pathways crucial for normal embryogenesis. However, detailed studies are needed to understand the long-term consequences of prenatal and foetal antidepressant exposure on embryonic growth and development. These changes may lead to abnormal growth patterns or congenital defects, emphasizing the need for caution when prescribing Venlafaxine during pregnancy. Keywords: Antidepressants, Venlafaxine, SNRI, Gallus gallus domesticus, Sonic Hedgehog (SHH), Protein Biochemistry, qRT-PCR

Sprouty2/4 deficiency disrupts early signaling centers impacting chondrogenesis in the mouse forelimb

Abstract The FGF signaling pathway plays an important role in the regulation of limb development, controlling cell migration, proliferation, differentiation, and apoptosis. Sprouty proteins act as antagonists of the FGF pathway and control the extent of FGF signaling as part of a negative feedback loop. Sprouty2/4 deficient mice evince defects in endochondral bone formation and digit patterning in their forelimbs, with pathogenesis recently related to ciliopathies. To understand the mechanisms behind these pathologies, the limb defects in Sprouty2+/−;Sprouty4−/− male and female mice were characterized and correlated to the dynamic expression patterns of Sprouty2 and Sprouty4, and the impact on the main signaling centers of the limb bud was assessed. Sprouty2 and Sprouty4 exhibited dynamic expressions during limb development. Interestingly, despite similar expression patterns in all limbs, the hindlimbs did not evince any obvious alterations in development, while the forelimbs showed consistent phenotypes of variable severity. Prenatally as well as postnatally, the left forelimb was significantly more severely affected than the right one. A broad variety of pathologies was present in the autopodium of the forelimb, including changes in digit number, size, shape, and number of bones, hand clefts, and digit fusions. Ectopic ossification of bones and abnormal bone fusions detected in micro-CT scans were frequently observed in the digital as well as in the carpal and metacarpal areas. Sprouty2+/−;Sprouty4−/− limb buds showed patchy loss of Fgf8 expression in the apical ectodermal ridge, and a loss of tissue underlying these regions. The zone of polarizing activity was also impacted, with lineage analysis highlighting a change in the contribution of Sonic hedgehog expressing cells. These findings support the link between Sproutys and Hedgehog signaling during limb development and highlight the importance of Sprouty2 and Sprouty4 in controlling early signaling centers in the limb.

Generation of a transgenic chicken line with reporters for limb bud mesenchyme and apical ectodermal ridge cells.

Cell type-specific reporter transgenic chicken lines are invaluable tools in developmental biology, allowing the visualization of dynamics and differentiation states of target cell types in living embryos. Here, we report the establishment of a new transgenic chicken line in which limb mesenchyme and apical ectodermal ridge (AER) cells are labeled with different fluorescent proteins in the embryos. The processes for generating the reporter line involved using tissue-specific promoters, the Tol2 transposon-mediated genomic integration, and clonal culture system of primordial germ cells. Employing the transgenic chickens would facilitate the detailed characterization of limb mesenchyme and AER cells. Thus, this reporter chicken line will be a powerful tool for advancing the study of vertebrate limb development.

Phenanthrene toxicity during early development of the neotropical tree frog Dendropsophus branneri.

Phenanthrene is considered a priority polycyclic aromatic hydrocarbon due to its ubiquitous presence in aquatic and terrestrial environments and its toxic potential. Tadpoles are sensitive ecotoxicological models that provide important information regarding effects of contaminants in amphibian species. The goal of the present study was to generate information regarding the acute and chronic toxicity of phenanthrene to the neotropical tree frog Dendropsophus branneri early life stages. Tadpoles at Gosner stage 25 were exposed to environmentally relevant concentrations of 10.8, 18.6, 76.2, 187.7, and 279.6 µg phenanthrene L-1 in two experiments with 15 and 60 days of exposure. Lethality, progression of development, final weight, swimming behavior and enzymatic biomarkers were analyzed. The lethal concentration of dissolved phenanthrene for 50 % of D. branneri tadpoles after 15 days of exposure was 154.8 µg L-1, typical of a sensitive species. Significant developmental delay was verified, with a lowest observed effect concentration (LOEC) of 76.2 µg L-1 and 10.8 µg L-1 after exposures of 15 and 60 days, respectively. Delay was measured based on the difference between the mean Gosner stage of controls and exposed tadpoles (Deltagosner). Deltagosner after 60 days of exposure ranged from 10 at 10.8 µg L-1 to 13 at 187.7 µg L-1, and tadpoles remained in the early stages of hind limb development (Gosner stages 28-32), in contrast to controls that reached stage 42 with fully formed forelimbs and hind limbs with toes at metamorphic climax. Glutathione-S-transferase and Catalase were induced in exposed tadpoles, possibly due to oxidative stress. Thigmotaxis was decreased in phenanthrene exposed tadpoles, indicating loss of anti-predatory behaviors. Final wet weight of exposed D.branneri tadpoles significantly decreased. Delayed development and slower growth rate are crucial factors for tadpole survival, and these effects of phenanthrene on D.branneri early stages potentially affects its recruitment to the adult stage.

Novel function of Hox13 in regulating outgrowth of the newt hindlimb bud through interaction with Fgf10 and Tbx4.

5'Hox genes regulate pattern formation along the axes of the limb. Previously, we showed that Hoxa13/Hoxd13 double-mutant newts lacked all digits of the forelimbs during development and regeneration, showing that newt Hox13 is necessary for digit formation in development and regeneration. In addition, we found another unique phenotype. Some of the Hox13 crispant newts showed hindlimb defects, in which whole or almost whole hindlimbs were lost, suggesting a novel function of Hox13 in limb development. Using germline mutants, we showed that mutation in Hox13 led to hindlimb defects. The limb buds of Hox13 crispants formed, however, did not show outgrowth. Expression of Fgf10 and Tbx4, which are involved in limb outgrowth, decreased in the hindlimb buds of Hox13 crispants. In addition, hindlimb defects were observed in both Fgf10 and Tbx4 crispant newts. Finally, Fgf10 and Tbx4 interacted with Hox13 genetically. Our results revealed a novel function of Hox13 in regulating the outgrowth of the newt hindlimb bud through interaction with Fgf10 and Tbx4.

INVESTIGATION OF SEX HORMONE CONCENTRATIONS IN MALE WHITE RATS AND THE QUANTITATIVE AND ANATOMICAL CHANGES IN THEIR OFFSPRING FOLLOWING CHRONIC HALOPERIDOL ADMINISTRATION

Objectives: To investigate the effects of chronic, dose-dependent haloperidol administration on the concentration of sex hormones (total testosterone (Ttotal), free testosterone (Tfree), follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PL), progesterone (PG), estriol (ER), estradiol (ED)), as well as fertilization rates, and the quantitative and anatomical parameters of offspring in male white rats. Materials and Methods. The study was conducted on 54 white rats (both sexes, weighing 170-190 g) housed at the Scientific Research Center of Azerbaijan Medical University. The animals were divided into three groups, each consisting of 12 male rats and 6 female rats. The effects of chronic haloperidol administration on sex hormone concentrations and the quantitative and anatomical parameters of the offspring were examined. Results. Chronic administration of haloperidol at doses of 0.5 mg/kg and 3 mg/kg to male white rats resulted in a statistically significant, dose-dependent decrease in the levels of sex hormones: Ttotal, Tfree, FSH, LH, PG, ER, and ED (except PL). In females mated with haloperidol-treated males, significant alterations in pregnancy outcomes were observed. Compared to the control group, haloperidol administration reduced the number of offspring, caused abnormalities in their appearance, led to stillbirths, and delayed the opening of the auditory canal and the formation of the primary hairline. Additionally, a “reverse geotaxis” reaction was observed in the offspring. Conclusion. Compared to the control group, 2 offspring were born in the group receiving chronic haloperidol at a dose of 0.5 mg/kg, while 3 offspring with congenital anomalies were born in the group receiving chronic haloperidol at a dose of 3 mg/kg. Significant changes in the course of pregnancy and visible deviations from the norm during childbirth were observed in females mated with male rats treated with haloperidol. Visual inspection of the offspring 24-48 hours after delivery revealed abnormalities, including asymmetry of the skull and facial skeleton, abnormal limb, tail, eye socket, nostril, and oral slit development, in both experimental groups.

Time to Amputation After Traumatic Digital Injury Does Not Affect Complication Rates: A Retrospective Multi-Institutional Analysis.

Revisionary digital amputations are often performed after partial or full traumatic digital amputation to minimize complications while preserving as much length and functionality as possible. Many surgeons attempt revisionary procedures swiftly after initial injury. The aim of this study was to investigate the effects of time from injury to surgery on rate of complications and reoperation in revisionary traumatic digital amputations. This was a retrospective chart review of all patients undergoing revisionary digital amputation for initial traumatic amputation at a single hospital from January 1, 2007 to December 31, 2021. Demographics, comorbidities, surgical details, complications, and time from injury to surgery were collected. Five-factor modified fragility index scores were also computed for each patient. Primary outcomes of interest included complications and need for additional procedures. Secondary outcomes of interest included development of neuroma, phantom limb, and referral to a long-term pain specialist. A total of 97 patients were identified as meeting all inclusion criteria. The average time to surgery was 14.4 days. Body mass index, comorbidities, and time to surgery were not associated with increased risk of complication. Increasing time to surgery was not significantly associated with increased risk of complications, development of neuroma, phantom limb, or a referral to long-term pain service. The only factors which were significantly associated with reoperation were absence of diabetes and hypertension. Increasing time to surgery after initial injury was not significantly associated with increased risk of complications or reoperation. Surgeons should consider this when assessing urgency of surgery in patients after traumatic digital amputation.

Crosstalk between paralogs and isoforms influences p63-dependent regulatory element activity.

The p53 family of transcription factors (p53, p63 and p73) regulate diverse organismal processes including tumor suppression, maintenance of genome integrity and the development of skin and limbs. Crosstalk between transcription factors with highly similar DNA binding profiles, like those in the p53 family, can dramatically alter gene regulation. While p53 is primarily associated with transcriptional activation, p63 mediates both activation and repression. The specific mechanisms controlling p63-dependent gene regulatory activity are not well understood. Here, we use massively parallel reporter assays (MPRA) to investigate how local DNA sequence context influences p63-dependent transcriptional activity. Most regulatory elements with a p63 response element motif (p63RE) activate transcription, although binding of the p63 paralog, p53, drives a substantial proportion of that activity. p63RE sequence content and co-enrichment with other known activating and repressing transcription factors, including lineage-specific factors, correlates with differential p63RE-mediated activities. p63 isoforms dramatically alter transcriptional behavior, primarily shifting inactive regulatory elements towards high p63-dependent activity. Our analysis provides novel insight into how local sequence and cellular context influences p63-dependent behaviors and highlights the key, yet still understudied, role of transcription factor paralogs and isoforms in controlling gene regulatory element activity.

Dr. Per-Ingvar Branemark: The Father of Modern Dental Implantology.

Swedish physician and anatomist Professor Per-Ingvar Brånemark (1929-2014), often known as Sir Brånemark, discovered the osseointegration phenomenon that revolutionized the dental implantology field. Even though he was an orthopedic surgeon, Sir Brånemark's groundbreaking contributions to dentistry in the form of the Brånemark System of dental implants established the groundwork for modern fixed prosthodontics. The dental community still values his efforts today. His influence has not only been seen in the realm of dentistry but also in medicine, where the phenomenon of osseointegration has led to the development of prosthetic limbs as well as the development of cochlear implants. Based on a thorough literature search conducted across many databases, including PubMed and Google Scholar, this study offers a scientific overview of Sir Brånemark's contribution to implantology. His legacy lives on through the Brånemark Osseointegration Centre (BOC), founded in 1989 in Gothenburg, Sweden.

Expression of distal limb patterning genes in Hypsibius exemplaris indicate regionalization and suggest distal identity of tardigrade legs

BackgroundPanarthropods, a major group of invertebrate animals comprised of arthropods, onychophorans, and tardigrades, are the only limb-bearing members of Ecdysozoa. The complexity and versatility of panarthropod paired limbs has prompted great interest in their development to better understand the formation of these structures and the genes involved in this process. However, studies of limb patterning and development are overwhelmingly focused on arthropods, followed by select work on onychophorans but almost entirely lacking for tardigrades. This model organism bias is inherently limited and precludes a comparative analysis of how panarthropod legs originated, have evolved, and the likely limb patterning genes present in the earliest panarthropod ancestors. In this study, we investigated tardigrade homologs of seven arthropod distal limb patterning genes (apterous, aristaless, BarH1, clawless, Lim1, rotund, and spineless) to better characterize tardigrade limb development in a comparative context.ResultsWe detected homologs of all seven genes in the eutardigrade Hypsibius exemplaris and heterotardigrade Echiniscoides cf. sigismundi suggesting their conservation in both tardigrade lineages. Hybridization chain reaction experiments in H. exemplaris reveal a regionalized expression pattern for the genes aristaless, BarH1, clawless, rotund and spineless.ConclusionThe observed regionalized expression of the distal limb patterning genes in H. exemplaris might reflect the external morphological features of tardigrade legs, such as the distal claws, sensory organs in the proximal region, and specific muscle attachment sites. The comparison between the expression of these limb patterning genes in H. exemplaris relative to other panarthropods suggests their conserved role in the last common panarthropod ancestor, such as establishing the distal limb end and the distribution of sensory structures. Our results support the hypothesis that tardigrade legs are homologous to the distal region of other panarthropod limbs, as suggested by previous work on the expression of leg gap genes in H. exemplaris.

Small heterodimer partner-interacting leucine zipper protein suppresses pain and cartilage destruction in an osteoarthritis model by modulating the AMPK/STAT3 signaling pathway

ObjectiveOsteoarthritis (OA) is a degenerative joint disease caused by the breakdown of joint cartilage and adjacent bone. Joint injury, being overweight, differences in leg length, high levels of joint stress, abnormal joint or limb development, and inherited factors have been implicated in the etiology of OA. In addition to physical damage to the joint, a role for inflammatory processes has been identified as well. Small heterodimer partner-interacting leucine zipper protein (SMILE) regulates transcription and many cellular functions. Among the proteins activated by SMILE is the peroxisome proliferator-activated receptor (PPAR) γ, which mediates the activities of CD4 + T helper cells, including Th1, Th2, and Th17, as well as Treg cells. PPAR-γ binds to STAT3 to inhibit its transcription, thereby suppressing the expression of the NF-κB pathway, and in turn, the expression of the inflammatory cytokines interferon (IFN), interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, which are sub-signals of STAT3 and NF-κB.MethodsOA was induced in control C57BL/6 mice and in C57BL/6-derived SMILE-overexpressing transgenic (SMILE Tg) mice. The protein expression levels in the joint and spleen tissues were analyzed by immunohistochemistry and immunofluorescence images. In addition, flow cytometry was performed for detecting changes of the changes of immune cells.ResultsLess cartilage damage and significantly reduced levels of OA biomarkers (MMP13, TIMP3 and MCP-1) were observed in SMILE Tg mice. Immunohistochemistry performed to identify the signaling pathway involved in the link between SMILE expression and OA revealed decreased levels of IL-1β, IL-6, TNF-α, and phosphorylated AMPK in synovial tissues as well as a significant decrease in phosphorylated STAT3 in both cartilage and synovium. Changes in systemic immune cells were investigated via flow cytometry to analyze splenocytes isolated from control and SMILE Tg mice. SMILE Tg mice had elevated proportions of CD4 + IL-4 + cells (Th2) and CD4 + CD25 + Foxp3 + cells (Treg) and a notable decrease in CD4 + IL-17 + cells (Th17).ConclusionOur results show that overexpressed SMILE attenuates the symptoms of OA, by increasing AMPK signaling and decreasing STAT3, thus reducing the levels of inflammatory immune cells.

3D-environment and muscle contraction regulate the heterogeneity of myonuclei

Skeletal muscle formation involves tight interactions between muscle cells and associated connective tissue fibroblasts. Every muscle displays the same type of organisation, they are innervated in the middle and attached at both extremities to tendons. Myonuclei are heterogeneous along myotubes and regionalised according to these middle and tip domains. During development, as soon as myotubes are formed, myonuclei at muscle tips facing developing tendons display their own molecular program. In addition to molecular heterogeneity, a subset of tip myonuclei has a fibroblastic origin different to the classical somitic origin, highlighting a cellular heterogeneity of myonuclei in foetal myotubes. To gain insights on the functional relevance of myonucleus heterogeneity during limb development, we used 2D culture and co-culture systems to dissociate autonomous processes (occurring in 2D-cultures) from 3D-environment of tissue development. We also assessed the role of muscle contraction in myonucleus heterogeneity in paralysed limb muscles. The regionalisation of cellular heterogeneity was not observed in 2D cell culture systems and paralyzed muscles. The molecular signature of MTJ myonuclei was lost in a dish and paralysed muscles indicating a requirement of 3D-enviroment and muscle contraction for MTJ formation. Tip genes that maintain a regionalized expression at myotube tips in cultures are linked to sarcomeres. The behaviour of regionalized markers in cultured myotubes and paralyzed muscles allows us to speculate whether the genes intervene in myogenesis, myotube attachment or MTJ formation.

Convergent Degenerated Regulatory Elements Associated with Limb Loss in Limbless Amphibians and Reptiles.

Limbs are a defining characteristic of tetrapods, yet numerous taxa, primarily among amphibians and reptiles, have independently lost limbs as an adaptation to new ecological niches. To elucidate the genetic factors contributing to this convergent limb loss, we present a 12 Gb chromosome-level assembly of the Banna caecilian (Ichthyophis bannanicus), a limbless amphibian. Our comparative analysis, which includes the reconstruction of amphibian karyotype evolution, reveals constrained gene length evolution in a subset of developmental genes across 3 large genomes. Investigation of limb development genes uncovered the loss of Grem1 in caecilians and Tulp3 in snakes. Interestingly, caecilians and snakes share a significantly larger number of convergent degenerated conserved noncoding elements than limbless lizards, which have a shorter evolutionary history of limb loss. These convergent degenerated conserved noncoding elements overlap significantly with active genomic regions during mouse limb development and are conserved in limbed species, suggesting their essential role in limb patterning in the tetrapod common ancestor. While most convergent degenerated conserved noncoding elements emerged in the jawed vertebrate ancestor, coinciding with the origin of paired appendage, more recent degenerated conserved noncoding elements also contribute to limb development, as demonstrated through functional experiments. Our study provides novel insights into the regulatory elements associated with limb development and loss, offering an evolutionary perspective on the genetic basis of morphological specialization.

Development of a ZRS Reporter System for the Newt (Cynops pyrrhogaster) During Terrestrial Limb Regeneration.

Newts, a type of urodele amphibian, offer remarkable insights into regenerative medicine due to their extraordinary tissue regeneration capabilities-a challenging feat in humans. During limb regeneration of adult newts, fascinating cellular and molecular processes are revealed, including scarless healing, de-differentiation of mature cells, and regeneration of limbs and digits. Sonic hedgehog (Shh), crucial for vertebrate limb development, is regulated by the zone of polarizing activity regulatory sequence (ZRS) in the limb bud zone of polarizing activity (ZPA). The metamorphosed (terrestrial) newt can reactivate Shh during regeneration, facilitating proper limb patterning. Cell types capable of regulating the ZRS in metamorphosed newts remain unknown. The identification of such cell types provides invaluable insight into novel regenerative mechanisms. In this study, we developed the first newt ZRS reporter. We isolated and characterized the newt ZRS enhancer (nZRS), identifying conserved DNA binding sites. Several binding sites with medical relevance were conserved in the newt ZRS. In functional analysis, we developed a system composed of a transgenic nZRS reporter newt and a new newt anti-Shh antibody, which allowed Shh monitoring during limb regeneration. We identified a group of Schwann cells capable of ZRS reporter and Shh protein expression during terrestrial limb regeneration. This system provides a valuable in vivo approach for future genetic studies of patterning during limb regeneration.

New insight into the development of synpolydactyly caused by expansion of HOXD13 polyalanine based on weighted gene co-expression network analysis

BackgroundSynpolydactyly (SPD) is mainly caused by mutations of polyalanine expansion (PAE) in the transcription factor gene HOXD13 and the involved cell types and signal pathway are still not clear possible pathways and single-cell expression characteristics of limb bud in HOXD13 PAE mice was analyzed in this study.MethodWe investigated a previous study of a mouse model with SPD and conducted weighted gene co-expression network analysis (WGCNA) using a single-cell RNA sequencing dataset from limb bud cells of SPD mouse model of HOXD13 + 7A heterozygote.ResultsAnalysis of WGCNA revealed that synpolydactyly-associated Hoxd13 PAEs alter the immune response and osteoclast differentiation, and enhance DNA replication. Bmp4, Hand2, Hoxd12, Lnp, Prrx1, Gmnn, and Cdc6 were found to play potentially key roles in synpolydactyly.ConclusionsThese findings evaluated the main genes related to SPD with PAE mutations in HOXD13 and advance our understanding of human limb development.

A novel genetic mouse model of osteoporosis with double heterozygosity of Irx3 and Irx5 characterizes sex-dependent phenotypes in bone homeostasis

Iroquois homeobox gene 3 (Irx3) and Irx5 encode transcription factors that play crucial roles in limb development and bone formation. Previous studies using knockout mice have revealed a role of Irx3 and Irx5 in osteogenesis in young adult mice. However, whether these genes are also essential for bone homeostasis in adulthood and contribute to bone diseases remain poorly understood. Osteoporosis is a disease characterized by lower bone mineral density and disrupted bone microarchitecture, typically occurs in postmenopausal women. Here, we demonstrate that Irx3/5dHet mice with a half-reduction of Irx3 and Irx5 dosage serve as a novel model of osteoporosis. By micro-computed tomography, we found that Irx3/5dHet mice exhibited sex-dependent bone loss patterns. While male Irx3/5dHet mice progressively lost trabecular microstructures with aging, female mutants exhibited lower bone mineral density (BMD) and bone volume fraction (BV/TV) at early adulthood (9–15 weeks old) but without further loss later at 1 year of age. Bone marrow adipocytes are known to be elevated at the expenses of lower osteogenesis in osteoporotic bone marrow. Surprisingly, we found sex-dependent changes in adipogenesis at the age of skeletal maturity that bone marrow adipocytes were reduced in female Irx3/5dHet mice along with deteriorated osteogenesis, while male mice exhibited elevated adipogenesis. In summary, we reported a novel genetic model for osteoporosis-like phenotypes, highlighting sex-dependent bone mineral density and bone marrow adipocyte characteristics.

A gene desert required for regulatory control of pleiotropic Shox2 expression and embryonic survival

Approximately a quarter of the human genome consists of gene deserts, large regions devoid of genes often located adjacent to developmental genes and thought to contribute to their regulation. However, defining the regulatory functions embedded within these deserts is challenging due to their large size. Here, we explore the cis-regulatory architecture of a gene desert flanking the Shox2 gene, which encodes a transcription factor indispensable for proximal limb, craniofacial, and cardiac pacemaker development. We identify the gene desert as a regulatory hub containing more than 15 distinct enhancers recapitulating anatomical subdomains of Shox2 expression. Ablation of the gene desert leads to embryonic lethality due to Shox2 depletion in the cardiac sinus venosus, caused in part by the loss of a specific distal enhancer. The gene desert is also required for stylopod morphogenesis, mediated via distributed proximal limb enhancers. In summary, our study establishes a multi-layered role of the Shox2 gene desert in orchestrating pleiotropic developmental expression through modular arrangement and coordinated dynamics of tissue-specific enhancers.

Apraxia phenotypes and frontotemporal lobar degeneration

BackgroundApraxia has been identified in all clinical forms of frontotemporal lobar degeneration (FTLD). The characteristics of apraxia symptoms and their underlying cognitive/motor basis are not fully understood. This study investigated apraxia in pathological subtypes of FTLD.MethodsThe study constituted a retrospective review of 115 pathologically confirmed cases of FTLD from a single cognitive neurology centre. Patients in whom apraxia had been documented as a notable clinical characteristic were identified. Apraxia features, demographic, cognitive, neurological, and imaging findings were recorded.ResultsEighteen patients were identified: 12 with FTLD-tau pathology (7 corticobasal degeneration (CBD), four Pick type and one progressive supranuclear palsy (PSP)) and six with FTLD-TDP pathology, all type A and four linked to progranulin gene mutations. Apraxia as a dominant presenting feature was typically associated with tau pathologies, whereas it emerged in the context of aphasia in TDP pathology. Apraxia typically predominated in one body part (face or limb) in tau but not TDP pathology. Relatively preserved activities in daily life were associated with TDP. Apraxia of speech was associated with tau pathology. Pick-type pathology was linked to symmetrical atrophy and late development of limb rigidity.ConclusionApraxia in FTLD subtypes has variable characteristics. Apraxia associated with CBD pathology conformed to criteria for probable corticobasal syndrome (CBS), whereas apraxia with Pick-type pathology did not. Apraxia in patients with TDP-A pathology was interpreted as one manifestation of their generalised communication disorder. Apraxia in FTLD may have distinct cognitive and motor substrates that require prospective investigation.

The functional roles of zebrafish HoxA- and HoxD-related clusters in the pectoral fin development

The paralogs 9–13 Hox genes in mouse HoxA and HoxD clusters are critical for limb development. When both HoxA and HoxD clusters are deleted in mice, significant limb truncation is observed compared to the phenotypes of single and compound mutants of Hox9-13 genes in these clusters. In zebrafish, mutations in hox13 genes in HoxA- and HoxD-related clusters result in abnormal morphology of pectoral fins, homologous to forelimbs. However, the effect of the simultaneous deletions of entire HoxA- and HoxD-related clusters on pectoral fin development remains unknown. Here, we generated mutants with several combinations of hoxaa, hoxab, and hoxda cluster deletions and analyzed the pectoral fin development. In hoxaa−/−;hoxab−/−;hoxda−/− larvae, the endoskeletal disc and the fin-fold are significantly shortened in developing pectoral fins. In addition, we show that this anomaly is due to defects in the pectoral fin growth after the fin bud formation. Furthermore, in the surviving adult mutants, micro-CT scanning reveals defects in the posterior portion of the pectoral fin which is thought to represent latent regions of the limb. Our results further support that the functional role of HoxA and HoxD clusters is conserved in the paired appendage formation in bony fishes.

8519 Investigating the Role of Protein Inhibitor of Activated STAT1 (Pias1) in Growth Plate Chondrocyte Maturation

Abstract Disclosure: J. Baronas: None. U. Ahmed: None. J.N. Hirschhorn: None. N.E. Renthal: None. Development of growth plate chondrocytes is a complex process that involves a wide array of regulatory elements. Recently our laboratory conducted a genome wide CRISPR knockout (KO) screen of growth plate chondrocyte maturation to discover novel genes and gene networks in the proliferation and maturation of chondrocytes. Among targets uncovered is Protein Inhibitor of Activated STAT 1 (Pias1), an E3 SUMO ligase that plays a multi-faceted role in genetic regulation, driving post-translational modifications, directly binding to transcription factors, and functioning as a DNA-binding protein. While Pias1 has been shown to be involved in the regulation of many cellular processes across multiple tissues, its function in growth plate development and chondrocyte maturation has been previously unstudied. In our genome-wide screen, our laboratory identified that loss of Pias1 led to early maturation of chondrocytes. This project seeks to investigate the role of Pias1 in chondrocyte maturation and differentiation. We first developed a Pias1-KO chondrocyte cell line, observing upregulation of hypertrophic markers Cd200 and Col10a1 in KOs relative to control via qPCR, in addition to proliferative regulators IHH and Pth1R. Through Bulk-RNAseq of the same cell line, we identified additional chondrocyte markers as upregulated in KO, as well as osteoblast marker Sp7. Members of the HoxD family, regulators of limb development, were downregulated. Cell culture data suggests that loss of Pias1 leads to increased cell proliferation and increased matrix production, indicating dysregulation of multiple chondrocyte processes. Immunohistochemistry of micromass culture sections also suggests morphological differences between KO and control, with KO cells significantly larger in diameter. Early SUMO-1 profiling yields limited evidence of decreased global SUMOylation in KO cells, one possible mechanistic explanation for the observed dysregulation. Ongoing studies are focused on identifying specific SUMOylation targets of Pias1 in chondrocytes, analyzing proteomic differences in KO and control, seeking putative DNA-binding sites of Pias1, and observing in vivo murine Pias1-KO growth plates. Our findings suggest that PIAS1 plays a crucial role in the growth plate by prolonging growth and delaying terminal hypertrophy. Our study aims to provide a better understanding of the regulatory pathways involved in growth plate development and related phenotypes such as height, and contribute to the development of novel therapies for growth-related disorders, such as achondroplasia and hypochondroplasia. Presentation: 6/1/2024