The role of the extracellular matrix in skeletal development

Temporal Transcriptomic Profiling Reveals Dynamic Changes in Gene Expression of Giant Freshwater Prawn upon Acute Saline-Alkaline Stresses

Bicarbonate and sulfate are among two primary ion constituents of saline-alkaline water, with excessive levels potentially causing metabolic disorders in crustaceans, affecting their molting and interrupting development. As an economically important crustacean species, the molecular adaptive mechanism of giant freshwater prawn Macrobrachium rosenbergii in response to the stress of bicarbonate and sulfate remains unexplored. To investigate the mechanism underlying NaHCO3, Na2SO4, and mixed NaHCO3, Na2SO4 stresses, M. rosenbergii larvae were exposed to the above three stress conditions, followed by total RNA extraction and high-throughput sequencing at eight distinct time points (0, 4, 8, 12, 24, 48, 72, and 96 h). Subsequent analysis revealed 13, 16, and 13 consistently identified differentially expressed genes (DEGs) across eight time points under three stress conditions. These consistently identified DEGs were significantly involved in the Gene Ontology (GO) terms of chitin-based cuticle development, protein-carbohydrate complex, structural constituent of cuticle, carnitine biosynthetic process, extracellular matrix, and polysaccharide catabolic process, indicating that alkaline stresses might potentially impact the energy metabolism, growth, and molting of M. rosenbergii larvae. Particularly, the transcriptome data revealed that DEGs associated with energy metabolism, immunity, and amino acid metabolism were enriched across multiple time points under three stress conditions. These DEGs are linked to Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, including glycolysis/glucogenesis, amino sugar and nucleotide sugar metabolism, and lysine degradation. Consistent enrichment findings across the three stress conditions support conclusions above. Together, these insights are instrumental in enhancing our understanding of the molecular mechanisms underlying the alkaline response in M. rosenbergii larvae. Additionally, they offer valuable perspectives on the regulatory mechanisms of freshwater crustaceans amid saline-alkaline water development.

Genomic Determinants of Knee Joint Biomechanics: An Exploration into the Molecular Basis of Locomotor Function, a Narrative Review

In recent years, the nexus between genetics and biomechanics has garnered significant attention, elucidating the role of genomic determinants in shaping the biomechanical attributes of human joints, specifically the knee. This review seeks to provide a comprehensive exploration of the molecular basis underlying knee joint locomotor function. Leveraging advancements in genomic sequencing, we identified specific genetic markers and polymorphisms tied to key biomechanical features of the knee, such as ligament elasticity, meniscal resilience, and cartilage health. Particular attention was devoted to collagen genes like COL1A1 and COL5A1 and their influence on ligamentous strength and injury susceptibility. We further investigated the genetic underpinnings of knee osteoarthritis onset and progression, as well as the potential for personalized rehabilitation strategies tailored to an individual's genetic profile. We reviewed the impact of genetic factors on knee biomechanics and highlighted the importance of personalized orthopedic interventions. The results hold significant implications for injury prevention, treatment optimization, and the future of regenerative medicine, targeting not only knee joint health but joint health in general.

Control of tissue homeostasis by the extracellular matrix: Synthetic heparan sulfate as a promising therapeutic for periodontal health and bone regeneration

Proteoglycans are core proteins associated with carbohydrate/sugar moieties that are highly variable in disaccharide composition, which dictates their function. These carbohydrates are named glycosaminoglycans, and they can be attached to proteoglycans or found free in tissues or on cell surfaces. Glycosaminoglycans such as hyaluronan, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparin/heparan sulfate have multiple functions including involvement in inflammation, immunity and connective tissue structure, and integrity. Heparan sulfate is a highly sulfated polysaccharide that is abundant in the periodontium including alveolar bone. Recent evidence supports the contention that heparan sulfate is an important player in modulating interactions between damage associated molecular patterns and inflammatory receptors expressed by various cell types. The structure of heparan sulfate is reported to dictate its function, thus, the utilization of a homogenous and structurally defined heparan sulfate polysaccharide for modulation of cell function offers therapeutic potential. Recently, a chemoenzymatic approach was developed to allow production of many structurally defined heparan sulfate carbohydrates. These oligosaccharides have been studied in various pathological inflammatory conditions to better understand their function and their potential application in promoting tissue homeostasis. We have observed that specific size and sulfation patterns can modulate inflammation and promote tissue maintenance including an anabolic effect in alveolar bone. Thus, new evidence provides a strong impetus to explore heparan sulfate as a potential novel therapeutic agent to treat periodontitis, support alveolar bone maintenance, and promote bone formation.

Control of craniofacial development by the collagen receptor, discoidin domain receptor 2

Development of the craniofacial skeleton requires interactions between progenitor cells and the collagen-rich extracellular matrix (ECM). The mediators of these interactions are not well-defined. Mutations in the discoidin domain receptor 2 gene (DDR2), which encodes a non-integrin collagen receptor, are associated with human craniofacial abnormalities, such as midface hypoplasia and open fontanels. However, the exact role of this gene in craniofacial morphogenesis is not known. As will be shown, Ddr2-deficient mice exhibit defects in craniofacial bones including impaired calvarial growth and frontal suture formation, cranial base hypoplasia due to aberrant chondrogenesis and delayed ossification at growth plate synchondroses. These defects were associated with abnormal collagen fibril organization, chondrocyte proliferation and polarization. As established by localization and lineage-tracing studies, Ddr2 is expressed in progenitor cell-enriched craniofacial regions including sutures and synchondrosis resting zone cartilage, overlapping with GLI1 + cells, and contributing to chondrogenic and osteogenic lineages during skull growth. Tissue-specific knockouts further established the requirement for Ddr2 in GLI +skeletal progenitors and chondrocytes. These studies establish a cellular basis for regulation of craniofacial morphogenesis by this understudied collagen receptor and suggest that DDR2 is necessary for proper collagen organization, chondrocyte proliferation, and orientation.

Comprehensive Analyses of Bone and Cartilage Transcriptomes Evince Ion Transport, Inflammation and Cartilage Development-Related Genes Involved in Chickens’ Femoral Head Separation

Simple Summary

Femoral head necrosis (FHN) and other locomotor problems cause severe impacts on the poultry industry due to huge economic losses and reduced animal welfare. Femoral head separation (FHS), the initial phase of FHN, is usually a subclinical condition characterized by the detachment of articular cartilage from the bone. In this study, we aimed to identify genes and biological processes involved with FHS in broilers. A better understanding of the FHS molecular mechanisms can help to develop strategies to reduce this condition in chickens. Here, we described several genes that have their expression altered in the articular cartilage and femur when normal and FHS-affected animals were compared. Furthermore, genetic variants were found differing between the studied groups. Therefore, performing an integrated analysis of these datasets, we were able to detect genes and variants related to FHS in chickens. Some of them, such as SLC4A1, RHAG, ANK1, MKNK2, SPTB, ADA, C7 and EPB420 genes were highlighted and should be further explored to validate them as candidates to FHS and FHN in chickens and possibly in humans.

Abstract

Femoral head separation (FHS) is usually a subclinical condition characterized by the detachment of articular cartilage from the bone. In this study, a comprehensive analysis identifying shared and exclusive expression profiles, biological processes (BP) and variants related to FHS in the femoral articular cartilage and growth plate in chickens was performed through RNA sequencing analysis. Thirty-six differentially expressed (DE) genes were shared between femoral articular cartilage (AC) and growth plate (GP) tissues. Out of those, 23 genes were enriched in BP related to ion transport, translation factors and immune response. Seventy genes were DE exclusively in the AC and 288 in the GP. Among the BP of AC, the response against bacteria can be highlighted, and for the GP tissue, the processes related to chondrocyte differentiation and cartilage development stand out. When the chicken DE genes were compared to other datasets, eight genes (SLC4A1, RHAG, ANK1, MKNK2, SPTB, ADA, C7 and EPB420) were shared between chickens and humans. Furthermore, 89 variants, including missense in the SPATS2L, PRKAB1 and TRIM25 genes, were identified between groups. Therefore, those genes should be more explored to validate them as candidates to FHS/FHN in chickens and humans.

The collagen receptor, discoidin domain receptor 2, functions in Gli1-positive skeletal progenitors and chondrocytes to control bone development

Discoidin Domain Receptor 2 (DDR2) is a collagen-activated receptor kinase that, together with integrins, is required for cells to respond to the extracellular matrix. Ddr2 loss-of-function mutations in humans and mice cause severe defects in skeletal growth and development. However, the cellular functions of Ddr2 in bone are not understood. Expression and lineage analysis showed selective expression of Ddr2 at early stages of bone formation in the resting zone and proliferating chondrocytes and periosteum. Consistent with these findings, Ddr2⁺ cells could differentiate into hypertrophic chondrocytes, osteoblasts, and osteocytes and showed a high degree of colocalization with the skeletal progenitor marker, Gli1. A conditional deletion approach showed a requirement for Ddr2 in Gli1-positive skeletal progenitors and chondrocytes but not mature osteoblasts. Furthermore, Ddr2 knockout in limb bud chondroprogenitors or purified marrow-derived skeletal progenitors inhibited chondrogenic or osteogenic differentiation, respectively. This work establishes a cell-autonomous function for Ddr2 in skeletal progenitors and cartilage and emphasizes the critical role of this collagen receptor in bone development.

Effects of organic macro and trace minerals in fast and slower growing broiler breeders' diet on offspring growth performance and tibia characteristics

This study was designed to evaluate effects of source of macro and trace minerals (inorganic vs. organic) in fast and slower growing broiler breeders' diets on egg and hatchling mineral content and on offspring tibia morphological, biophysical, and mechanical characteristics. After 10 wk feeding the breeders (at 30 wk of age), eggs were collected and incubated. Eggs and hatchlings were analysed on mineral content. Male chickens were assigned to 32 pens with 12 chickens per pen. At approximately 1,700 and 2,600 gram BW, three chickens per pen were slaughtered. Tibia characteristics were determined. Organic minerals in the broiler breeder diet resulted in higher Fe and Se concentration in the egg and in higher Se concentration in the hatchling. Despite effects of mineral source on mineral concentration in the eggs and hatchlings were limited, organic minerals in the slower-growing broiler breeder diet resulted in higher offspring BW (d 42, Δ = 115 g; P = 0.03) and advanced tibia development (higher thickness (∆ = 0.38 cm; P < 0.001), osseous volume (∆ = 5.1 cm³; P = 0.01), and mineral density (Δ = 0.13 g/cm³; P = 0.03) at 2,600 g BW), but this was not observed in fast-growing chickens. This suggests that 1) the difference in feed intake of the breeders between strains might affect offspring performance, which might indicate that current slower-growing breeder diets might be suboptimal in minerals or that transgenerational mineral availability in slower growing chickens appears to be more effective on bone development, which might be related to time available for bone development. 2) transgenerational mineral availability in offspring appears to play a role via other mechanisms than via absolute mineral concentrations.

Effects of barrier perch access and early dietary protein and energy dilution on some welfare parameters, tibiotarsus measurements, fear and mobility level in broiler chickens

1. This experiment determined the effect of increasing mobility in broiler chickens by placing barrier perches between feeders and drinkers. In addition, the limitation of early weight gain by dietary energy and protein dilution on some welfare parameters, tibiotarsus measurements, fear and mobility level was examined.2. A total of 504 male, one-day-old broiler chickens (Ross 308) were randomly allocated to four treatments with three replicate pens per treatment and 42 broiler chickens per pen as a 2 × 2 factorial arrangement. Treatments included feeding the basal control diet between 0-42 days or a diet diluted by 10% energy and 20% crude protein fed between 0-21 d, with the control diet fed between 22-42 d. The second factor was the presence or absence of barrier perches. All treatments were allocated as a completely randomised design. Welfare parameters (foot pad dermatitis, hock burn, gait score, feather score, breast blister), tibiotarsus measurements (bone mineral content, bone mineral density, fluctuating asymmetry and relative fluctuating asymmetry), tonic immobility and mobility level were recorded.3. Results showed that access to a barrier perch and the diluted diet increased the mobility in broiler chickens. However, access to a barrier perch had no significant effect on tibiotarsus and welfare parameters. Broiler chickens had better gait scores (P < 0.05) and lower foot pad dermatitis incidence (P < 0.01) in groups fed the diluted diet. The diluted diet had no significant effect on bone mineral density but reduced the tibiotarsus bone mineral content (P < 0.05).4. In conclusion, the diluted diet provided positive effects in terms of leg health due to weight gain limitations in the early period, thus improving broiler chicken welfare.

Histomorphometric, Immunohistochemical, Ultrastructural Characterization of a Nano-Hydroxyapatite/Beta-Tricalcium Phosphate Composite and a Bone Xenograft in Sub-Critical Size Bone Defect in Rat Calvaria

Nowadays, we can observe a worldwide trend towards the development of synthetic biomaterials. Several studies have been conducted to better understand the cellular mechanisms involved in the processes of inflammation and bone healing related to living tissues. The aim of this study was to evaluate tissue behaviors of two different types of biomaterials: synthetic nano-hydroxyapatite/beta-tricalcium phosphate composite and bone xenograft in sub-critical bone defects in rat calvaria. Twenty-four rats underwent experimental surgery in which two 3 mm defects in each cavity were tested. Rats were divided into two groups: Group 1 used xenogen hydroxyapatite (Bio Oss™); Group 2 used synthetic nano-hydroxyapatite/beta-tricalcium phosphate (Blue Bone™). Sixty days after surgery, calvaria bone defects were filled with biomaterial, animals were euthanized, and tissues were stained with Masson’s trichrome and periodic acid–Schiff (PAS) techniques, immune-labeled with anti-TNF-α and anti-MMP-9, and electron microscopy analyses were also performed. Histomorphometric analysis indicated a greater presence of protein matrix in Group 2, in addition to higher levels of TNF-α and MMP-9. Ultrastructural analysis showed that biomaterial fibroblasts were associated with the tissue regeneration stage. Paired statistical data indicated that Blue Bone™ can improve bone formation/remodeling when compared to biomaterials of xenogenous origin.

Manganese requirements of broiler breeder hens

The present research was conducted to assess Mn requirements of broiler breeder hens. One hundred and twenty Cobb 500 hens, 22 wk of age, were individually allocated in cages. After fed a Mn-deficient diet (22.2 ppm), hens were randomly placed in treatments having 6 increments of 30-ppm Mn. All trace minerals were from laboratory grade sources being Mn from Mn sulfate (MnSO₄H₂O). Treatments were fed for 4 periods of 28 d. There were no interactions between dietary Mn and period for any evaluated response (P > 0.05). Requirements of Mn for hen day egg production and settable egg production were 115.8 and 56.6 ppm and 122.1 and 63.6 ppm (P < 0.05), respectively, using quadratic polynomial (QP) and broken line quadratic (BLQ) models, whereas total eggs and total settable eggs per hen had Mn requirements estimated at 115.7 and 56.6 and 121.8 and 61.7 ppm (P < 0.05), respectively. Number of cracked, defective, and contaminated eggs decreased, whereas hatchability, hatchability of fertile eggs, eggshell percentage, and eggshell palisade layer increased when hens were fed diets having 48.5 to 168.2-ppm Mn (P < 0.05). Maximum responses for egg weight and eggshell percentage were 117.7 and 63.6 ppm as well as 131.6 and 71.0 ppm (P < 0.05), respectively, using QP and BLQ models. Breaking strength and egg specific gravity had Mn requirements estimated at 140.2 and 112.7 ppm as well as 131.3 68.5 ppm (P < 0.05), whereas eggshell palisade layer and eggshell thickness were maximized with 128.8 and 68.8 ppm and 140.2 134.2 ppm, respectively, for QP and BLQ models (P < 0.05). Maximum yolk Mn content values were obtained using 118.0- and 118.4-ppm Mn by QP and BLQ models, respectively. The average Mn requirements estimated for QP and BLQ models is 128.4 and 92.3 ppm Mn (18.7 and 13.5 mg/hen/d), respectively, which is much lower than what has been currently recommended in commercial production.

Effects of dietary organic minerals, fish oil, and hydrolyzed collagen on growth performance and tibia characteristics of broiler chickens

Nutrition is a crucial factor for growth and bone development in broiler chickens. Adjustments in dietary ingredients might affect bone development and consequently locomotion related problems. This study was designed to evaluate effects of dietary organic minerals (ORM), fish oil (FISH), and hydrolyzed collagen (COL) on growth performance and tibia characteristics of broiler chickens. A total of three hundred eighty four 1-day-old Ross 308 male broiler chickens were used in a complete randomized block design with 4 diet groups and 8 replicates per diet group. In the ORM diet, the inorganic macro and trace minerals were replaced by their organic varieties. In the FISH diet, palm oil and soybean oil were partly replaced by FISH. In the COL diet, soybean meal was partly replaced by COL. Results showed that the ORM and COL diet groups reached a higher body weight (BW) at 42 D of age than the FISH diet group, whereas the control group was in between. The feed conversion ratio between day 1 and 42 was lower in the ORM and COL diet groups than in both other diet groups. On day 28, 35, and 42, gait score (GS), Varus Valgus deformity, tibia length (TL), thickness, femoral and metatarsal head thickness (THT), mineral content (TMC), mineral density (TMD), breaking strength (TBS), stiffness (TSF), and energy to fracture (TEF) were measured (n = 3/replicate). The ORM diet group had higher TL at day 42, higher THT at day 28, higher TMC at day 42, higher TMD at day 28, 35, and 42, higher TBS at day 42, higher TSF at day 35 and 42, and higher TEF at day 42 compared to the FISH diet group, with the COL and control diet groups in between. It can be concluded that replacing dietary inorganic macro and trace minerals by their organic varieties seems to stimulate tibia dimensions, strength, and mineral content of broiler chickens. On the contrary, FISH appears to negatively affect tibia characteristics.

Effects of eggshell temperature pattern during incubation on tibia characteristics of broiler chickens at slaughter age

This study was designed to determine effects of eggshell temperature (EST) pattern in week 2 and week 3 of incubation on tibia development of broiler chickens at slaughter age. A total of 468 Ross 308 eggs were incubated at an EST of 37.8°C from incubation day (E) 0 to E7. Thereafter, a 2 × 2 factorial arrangement with 2 EST (37.8°C and 38.9°C) from E8 to E14 and 2 EST (36.7°C and 37.8°C) from E15 till hatch was applied. After hatching, chickens were reared until slaughter age with the 4 EST treatments and 8 replicates per treatment. At day 41 and 42, one male chicken per replicate per day was selected, and hock burn and food pad dermatitis were scored. Rotated tibia, tibia dyschondroplasia, epiphyseal plate abnormalities, bacterial chondronecrosis with osteomyelitis, and epiphysiolysis were assessed. Tibia weight, length, thickness, head thickness, and robusticity index were determined. X-ray analyses (osseous volume, pore volume, total volume, volume fraction, mineral content, and mineral density) and a 3-point bending test (ultimate strength, yield strength, stiffness, energy to fracture, and elastic modulus) were performed. A high EST (38.9°C) in week 2 of incubation, followed by a normal EST (37.8°C) in week 3 resulted in higher mineral content (P = 0.001), mineral density (P = 0.002), ultimate strength (P = 0.04), yield strength (P = 0.03), and stiffness (P = 0.05) compared with the other 3 EST groups (week 2 × week 3 interaction). A high EST (38.9°C) in week 2 of incubation, regardless of the EST in week 3, resulted in a higher tibia weight (P < 0.001), thickness (P = 0.05), osseous volume (P < 0.001), and total volume (P < 0.001) than a normal EST (37.8°C). It can be concluded that 1.1°C higher EST than normal in week 2 of incubation appears to stimulate tibia morphological, biophysical, and mechanical characteristics of broiler chickens at slaughter age. Additionally, a 1.1°C lower EST in week 3 of incubation appears to have negative effects on tibia characteristics, particularly in interaction with the EST in week 2 of incubation.

Proximal femoral head transcriptome reveals novel candidate genes related to epiphysiolysis in broiler chickens

BACKGROUND

The proximal femoral head separation (FHS) or epiphysiolysis is a prevalent disorder affecting the chicken femur epiphysis, being considered a risk factor to infection which can cause bacterial chondronecrosis with osteomyelitis in broilers. To identify the genetic mechanisms involved in epiphysiolysis, differentially expressed (DE) genes in the femur of normal and FHS-affected broilers were identified using RNA-Seq technology. Femoral growth plate (GP) samples from 35-day-old commercial male broilers were collected from 4 healthy and 4 FHS-affected broilers. Sequencing was performed using an Illumina paired-end protocol. Differentially expressed genes were obtained using the edgeR package based on the False Discovery Rate (FDR < 0.05).

RESULTS

Approximately 16 million reads/sample were generated with 2 × 100 bp paired-end reads. After data quality control, approximately 12 million reads/sample were mapped to the reference chicken genome (Galgal5). A total of 12,645 genes were expressed in the femur GP. Out of those, 314 were DE between groups, being 154 upregulated and 160 downregulated in FHS-affected broilers. In the functional analyses, several biological processes (BP) were overrepresented. Among them, those related to cell adhesion, extracellular matrix (ECM), bone development, blood circulation and lipid metabolism, which are more related to chicken growth, are possibly involved with the onset of FHS. On the other hand, BP associated to apoptosis or cell death and immune response, which were also found in our study, could be related to the consequence of the FHS.

CONCLUSIONS

Genes with potential role in the epiphysiolysis were identified through the femur head transcriptome analysis, providing a better understanding of the mechanisms that regulate bone development in fast-growing chickens. In this study, we highlighted the importance of cell adhesion and extracellular matrix related genes in triggering FHS. Furthermore, we have shown new insights on the involvement of lipidemia and immune response/inflammation with FHS in broilers. Understanding the changes in the GP transcriptome might support breeding strategies to address poultry robustness and to obtain more resilient broilers.

A recessive lethal chondrodysplasia in a miniature zebu family results from an insertion affecting the chondroitin sulfat domain of aggrecan

Background

Congenital skeletal malformations represent a heterogeneous group of disorders affecting bone and cartilage development. In cattle, particular chondrodysplastic forms have been identified in several miniature breeds. In this study, a phenotypic characterization was performed of an affected Miniature Zebu calf using computed tomography, necropsy and histopathological examinations, whole genome sequencing of the case and its parents on an Illumina NextSeq 500 in 2 × 150 bp paired-end mode and validation using Sanger sequencing and a Kompetitive Allele Specific PCR assay. Samples from the family of an affected Miniature Zebu with bulldog syndrome including parents and siblings, 42 healthy Miniature Zebu not related with members of the herd and 88 individuals from eight different taurine cattle breeds were available for validation.

Results

A bulldog-like Miniature Zebu calf showing a large bulging head, a short and compressed body and extremely short and stocky limbs was delivered after a fetotomy. Computed tomography and necropsy revealed severe craniofacial abnormalities including a shortening of the ventral nasal conchae, a cleft hard palate, rotated limbs as well as malformed and fused vertebrae and ribs. Histopathologic examination showed a disorganization of the physeal cartilage with disorderly arranged chondrocytes in columns and a multifocal closed epiphyseal plate. Whole-genome sequencing of this malformed Miniature Zebu calf, its dam and sire and subsequent comparative sequence analysis revealed a one base pair insertion (ACAN:c.5686insC) located within the cartilage development gene aggrecan (ACAN) exclusively homozygous in the affected calf and heterozygous in its parents. This variant was predicted to cause a frameshift (p.Val1898fsTer9) and thus a truncation of the chondroitin sulfate domain as well as a loss of the C-terminal globular domain of ACAN. It perfectly co-segregated with the lethal bulldog syndrome in Miniature Zebus.

Conclusions

We found a novel mutation in ACAN causing a recessive lethal chondrodysplasia in Miniature Zebu cattle. A diagnostic test for this mutation is now available for Miniature Zebu breeders preventing further cases of bulldog syndrome by targeted matings. To the authors’ best knowledge, this is the first case of a Miniature Zebu associated with an ACAN mutation.

Electronic supplementary material

The online version of this article (10.1186/s12863-018-0678-8) contains supplementary material, which is available to authorized users.

Associations among gait score, production data, abattoir registrations, and postmortem tibia measurements in broiler chickens

Lameness and impaired walking ability in rapidly growing meat-type broiler chickens are major welfare issues that cause economic losses. This study analyzed the prevalence of impaired walking and its associations with production data, abattoir registrations, and postmortem tibia measurements in Norwegian broiler chickens. Gait score (GS) was used to assess walking ability in 59 different commercial broiler flocks (Ross 308) close to the slaughter d, 5,900 broilers in total, in 3 different geographical regions. In each flock, 100 arbitrary broilers were gait scored and 10 random broilers were culled to harvest tibias. Abattoir registrations on flock level were collected after slaughter. A total of 24.6% of the broilers had moderate to severe gait impairment. The broilers were sampled in 2 stages, first slaughterhouse/region, and then owner/flock. The final models showed that impaired gait is associated with first-week mortality (P < 0.05), region (P < 0.001), height of tibias mid-shaft (P < 0.05), and calcium content in the tibia ash (P < 0.05), and negatively associated with DOA (P < 0.05). The prevalence of impaired gait indicates that this is a common problem in the broiler industry in Norway, although the mean slaughter age is only 31 d and the maximum allowed animal density is relatively low. Impaired walking ability could not be predicted by the welfare indicators footpad lesion score, total on-farm mortality, and decreasing DOA prevalence. Further studies are needed to explore the relationship between first-week mortality and gait score.

Irx3 and Bmp2 regulate mouse mesenchymal cell chondrogenic differentiation in both a Sox9-dependent and -independent manner

Sox9, a master regulator of cartilage development, controls the cell fate decision to differentiate from mesenchymal to chondrogenic cells. In addition, Sox9 regulates the proliferation and differentiation of chondrocytes, as well as the production of cartilage-specific proteoglycans. The existence of Sox9-independent mechanisms in cartilage development remains to be determined. Here, we attempted to identify genes involved in such putative mechanisms via microarray analysis using a mouse chondrogenic cell line, N1511. We first focused on transcription factors that exhibited upregulated expression following Bmp2 treatment, which was not altered by subsequent treatment with Sox9 siRNA. Among these, we selected positive regulators for chondrogenesis and identified Iroquois-related homeobox 3 (Irx3) as one of the candidate genes. Irx3 expression gradually increased with chondrocyte terminal differentiation in a reciprocal manner to Sox9 expression, and promoted the chondrogenic differentiation of mesenchymal cells upon Bmp2 treatment. Furthermore, Irx3 partially rescued impaired chondrogenesis by upregulating the expression of epiphycan and lumican under reduced Sox9 expression. Finally, Irx3 was shown to act in concert with Bmp2 signaling to activate the p38 MAPK pathway, which in turn stimulated Sox9 expression, as well as the expression of epiphycan and lumican in a Sox9-independent manner. These results indicate that Irx3 represents a novel chondrogenic factor of mesenchymal cells, acts synergistically with Bmp2-mediated signaling, and regulates chondrogenesis independent of the transcriptional machinery associated with Sox9-mediated regulation.

The genome of the largest bony fish, ocean sunfish (Mola mola), provides insights into its fast growth rate

BACKGROUND

The ocean sunfish (Mola mola), which can grow up to a length of 2.7 m and weigh 2.3 tons, is the world's largest bony fish. It has an extremely fast growth rate and its endoskeleton is mainly composed of cartilage. Another unique feature of the sunfish is its lack of a caudal fin, which is replaced by a broad and stiff lobe that results in the characteristic truncated appearance of the fish.

RESULTS

To gain insights into the genomic basis of these phenotypic traits, we sequenced the sunfish genome and performed a comparative analysis with other teleost genomes. Several sunfish genes involved in the growth hormone and insulin-like growth factor 1 (GH/IGF1) axis signalling pathway were found to be under positive selection or accelerated evolution, which might explain its fast growth rate and large body size. A number of genes associated with the extracellular matrix, some of which are involved in the regulation of bone and cartilage development, have also undergone positive selection or accelerated evolution. A comparison of the sunfish genome with that of the pufferfish (fugu), which has a caudal fin, revealed that the sunfish contains more homeobox (Hox) genes although both genomes contain seven Hox clusters. Thus, caudal fin loss in sunfish is not associated with the loss of a specific Hox gene.

CONCLUSIONS

Our analyses provide insights into the molecular basis of the fast growth rate and large size of the ocean sunfish. The high-quality genome assembly generated in this study should facilitate further studies of this 'natural mutant'.

Molecular cloning of a novel glucuronokinase/putative pyrophosphorylase from zebrafish acting in an UDP-glucuronic acid salvage pathway

In animals, the main precursor for glycosaminoglycan and furthermore proteoglycan biosynthesis, like hyaluronic acid, is UDP-glucuronic acid, which is synthesized via the nucleotide sugar oxidation pathway. Mutations in this pathway cause severe developmental defects (deficiency in the initiation of heart valve formation). In plants, UDP-glucuronic acid is synthesized via two independent pathways. Beside the nucleotide sugar oxidation pathway, a second minor route to UDP-glucuronic acid exist termed the myo-inositol oxygenation pathway. Within this myo-inositol is ring cleaved into glucuronic acid, which is subsequently converted to UDP-glucuronic acid by glucuronokinase and UDP-sugar pyrophosphorylase. Here we report on a similar, but bifunctional enzyme from zebrafish (Danio rerio) which has glucuronokinase/putative pyrophosphorylase activity. The enzyme can convert glucuronic acid into UDP-glucuronic acid, required for completion of the alternative pathway to UDP-glucuronic acid via myo-inositol and thus establishes a so far unknown second route to UDP-glucuronic acid in animals. Glucuronokinase from zebrafish is a member of the GHMP-kinase superfamily having unique substrate specificity for glucuronic acid with a K_m of 31±8 µM and accepting ATP as the only phosphate donor (K_m: 59±9 µM). UDP-glucuronic acid pyrophosphorylase from zebrafish has homology to bacterial nucleotidyltransferases and requires UTP as nucleosid diphosphate donor. Genes for bifunctional glucuronokinase and putative UDP-glucuronic acid pyrophosphorylase are conserved among some groups of lower animals, including fishes, frogs, tunicates, and polychaeta, but are absent from mammals. The existence of a second pathway for UDP-glucuronic acid biosynthesis in zebrafish likely explains some previous contradictory finding in jekyll/ugdh zebrafish developmental mutants, which showed residual glycosaminoglycans and proteoglycans in knockout mutants of UDP-glucose dehydrogenase.

EQUILÍBRIO E PROBLEMAS LOCOMOTORES EM FRANGOS DE CORTE

O crescimento de uma ave depende particularmente do desenvolvimento muscular e do tecido ósseo. Atualmente em frangos de corte o crescimento muscular é extremamente elevado enquanto seu suporte esquelético ainda se encontra muito imaturo, tendo como consequências o aparecimento de afecções locomotoras entre outras. Com os avanços no melhoramento genético avícola, verifica-se que a forma de caminhar e a condição de equilíbrio foram influenciadas negativamente, causando dificuldades de locomoção nesses animais. A presente revisão apresenta as principais desordens locomotoras que acometem as aves de produção e alguns dos fatores que as influenciam, assim como o impacto que elas causam na avicultura de corte.

A genetical genomics approach reveals new candidates and confirms known candidate genes for drip loss in a porcine resource population

In this study lean meat water-holding capacity (WHC) of a Duroc × Pietrain (DuPi) resource population with corresponding genotypes and transcriptomes was investigated using genetical genomics. WHC was characterized by drip loss measured in M. longissimus dorsi. The 60K Illumina SNP chips identified genotypes of 169 F2 DuPi animals. Whole-genome transcriptomes of muscle samples were available for 132 F2 animals using the Affymetrix 24K GeneChip® Porcine Genome Array. Performing genome-wide association studies of transcriptional profiles, which are correlated with phenotypes, allows elucidation of cis- and trans-regulation. Expression levels of 1,228 genes were significantly correlated with drip loss and were further analyzed for enrichment of functional annotation groups as defined by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways. A hypergeometric gene set enrichment test was performed and revealed glycolysis/glyconeogenesis, pentose phosphate pathway, and pyruvate metabolism as the most promising pathways. For 267 selected transcripts, expression quantitative trait loci (eQTL) analysis was performed and revealed a total of 1,541 significant associations. Because of positional accordance of the gene underlying transcript and the eQTL location, it was possible to identify eight eQTL that can be assumed to be cis-regulated. Comparing the results of gene set enrichment and the eQTL detection tests, molecular networks and potential candidate genes, which seemed to play key roles in the expression of WHC, were detected. The α-1-microglobulin/bikunin precursor (AMBP) gene was assumed to be cis-regulated and was part of the glycolysis pathway. This approach supports the identification of trait-associated SNPs and the further biological understanding of complex traits.

The effects of growth rate on leg morphology and tibia breaking strength, mineral density, mineral content, and bone ash in broilers

Fast-growing broilers are especially susceptible to bone abnormalities, causing major problems for broiler producers. The cortical bones of fast-growing broilers are highly porous, which may lead to leg deformities. Leg problems were investigated in 6-wk-old Arkansas randombred broilers. Body weight was measured at hatch and at 6 wk. There were 8 different settings of approximately 450 eggs each. Two subpopulations, slow-growing (SG; bottom quarter, n=511) and fast-growing (FG; top quarter, n=545), were created from a randombred population based on their growth rate from hatch until 6 wk of age. At 6 wk of age, the broilers were processed and chilled at 4°C overnight before deboning. Shank (78.27±8.06 g), drum stick (190.92±16.91 g), and thigh weights (233.88±22.66 g) of FG broilers were higher than those of SG broilers (54.39±6.86, 135.39±15.45, and 168.50±21.13 g, respectivly; P<0.001). Tibia weights (15.36±2.28 g) of FG broilers were also greater than those of SG broilers (11.23±1.81 g; P<0.001). Shank length (81.50±4.71 g) and tibia length (104.34±4.45 mm) of FG broilers were longer than those of SG broilers (71.88±4.66 and 95.98±4.85 mm, respectively; P<0.001). Shank diameter (11.59±1.60 mm) and tibia diameter (8.20±0.62 mm) of FG broilers were wider than those of SG broilers (9.45±1.74, 6.82±0.58 mm, respectively; P<0.001). Tibia breaking strength (28.42±6.37 kg) of FG broilers was higher than those of SG broiler tibia (21.81±5.89 kg; P<0.001). Tibia density and bone mineral content (0.13±0.01 g/cm2 and 1.29±0.23 g, respectively) of FG broilers were higher than those of SG broiler tibia (0.11±0.01 g/cm2 and 0.79±0.1 g; P<0.001). Tibia percentage of ash content (39.76±2.81) of FG broilers was lower than that of SG broilers (39.99±2.67; P=0.173). Fast-growing broiler bones were longer, wider, heavier, stronger, more dense, and contained more ash than SG ones. After all parameters were calculated per unit of final BW at 6 wk, tibia density and bone ash percentage of FG broilers were lower than those of SG broilers.

Structural and molecular analyses of bone bridge formation within the growth plate injury site and cartilage degeneration at the adjacent uninjured area

Injury to the growth plate is common and yet the injured cartilage is often repaired with undesirable bony tissue, leading to bone growth defects in children. Using a rat tibial growth plate injury model, our previous studies have shown sequential inflammatory, fibrogenic, osteogenic and bone maturation responses involved in the bony repair. However, it remains unclear whether there is progressive accumulation of bone within the injury site and any potential degenerative changes at the adjacent non-injured area of the growth plate. This study examined effects of growth plate injury on the structure, composition and some cellular and molecular changes at the injury site and adjacent uninjured area. Micro-CT analysis revealed that while the bone volume within the injury site at day 14 was small, the bone bridge was considerably larger at the injury site by 60 days post-injury. Interestingly, formation of bone bridges in the adjacent uninjured area was detected in 60% of injured animals at day 60. Immunohistochemical analyses revealed reduced chondrocyte proliferation (PCNA labelling) but increased apoptosis (nick translation labelling) in the adjacent uninjured area. RT-PCR analysis on adjacent uninjured growth plate tissue found increased expression of osteocalcin at day 60, differential expression of apoptosis-regulatory genes and alterations in genes associated with chondrocyte proliferation/differentiation, including Sox9 and IGF-I. Therefore, this study has demonstrated progressive changes in the structure/composition of the injury site and adjacent uninjured area and identified cellular and molecular alterations or degeneration in adjacent uninjured growth plate in response to injury.

Association and expression quantitative trait loci (eQTL) analysis of porcine AMBP, GC and PPP1R3B genes with meat quality traits

The aim of this research was to screen polymorphism and to perform association study of porcine AMBP (alpha-1-microglobulin/bikunin precursor), GC (group-specific component protein) and PPP1R3B (protein phosphatase 1, regulatory (inhibitor) subunit 3B) genes with meat quality traits as well as to unravel the transcriptional regulation of these genes by expression QTL (eQTL) study. For this purpose, Duroc × Pietrain F2 resource population (DuPi; n = 313) and a commercial breed Pietrain (Pi; n = 110) were used for association and only DuPi for expression and eQTL study. A SNP was identified in the genes AMBP (g.22229C>T), GC (g.398C>T) and PPP1R3B (c.479A>G), respectively. In DuPi SNP of AMBP was associated (P < 0.05) with meat colour, pH(1L), pH(24L), pH(24H) and conductivity(24L); SNP of GC showed tendency to association (P < 0.10) with pH24H, conductivity(1L) and thawing loss, and SNP of PPP1R3B was associated (P < 0.05) with meat colour, pH(1L), pH(24L), pH(24H) and shear force. In Pi SNPs of AMBP and GC was associated with pH(24H) and PPP1R3B SNP was associated with pH(24L). The mRNA levels in Longissimus dorsi muscle tissue of these three genes were evaluated by using qRT-PCR to identify association between gene expression and meat quality traits as well as to analyse eQTL. The mRNA expression of PPP1R3B associated with pH(24L) (P < 0.05). Expression of these three genes was higher in animals with low pH of muscle. Linkage analysis using QTL Express revealed ten trans-regulated eQTL on seven porcine autosomes. Suggestive eQTL [P < 0.05, CW (chromosome-wide)] were found for PPP1R3B on SSC3 and 13. These results revealed that genetic variation and gene expression of these genes are associated with the meat quality traits. These three genes could influence meat quality and could be potential positional, physiological and functional candidate gene for meat quality traits in pigs. However, the analysis of eQTL also suggested that we need to consider additional genes encoding for transcription factors (TF), via fine-mapping underlying the eQTL peaks, in order to understand interaction among these genes.

UDP xylose synthase 1 is required for morphogenesis and histogenesis of the craniofacial skeleton

UDP-xylose synthase (Uxs1) is strongly conserved from bacteria to humans, but because no mutation has been studied in any animal, we do not understand its roles in development. Furthermore, no crystal structure has been published. Uxs1 synthesizes UDP-xylose, which initiates glycosaminoglycan attachment to a protein core during proteoglycan formation. Crystal structure and biochemical analyses revealed that an R233H substitution mutation in zebrafish uxs1 alters an arginine buried in the dimer interface, thereby destabilizing and, as enzyme assays show, inactivating the enzyme. Homozygous uxs1 mutants lack Alcian blue-positive, proteoglycan-rich extracellular matrix in cartilages of the neurocranium, pharyngeal arches, and pectoral girdle. Transcripts for uxs1 localize to skeletal domains at hatching. GFP-labeled neural crest cells revealed defective organization and morphogenesis of chondrocytes, perichondrium, and bone in uxs1 mutants. Proteoglycans were dramatically reduced and defectively localized in uxs1 mutants. Although col2a1a transcripts over-accumulated in uxs1 mutants, diminished quantities of Col2a1 protein suggested a role for proteoglycans in collagen secretion or localization. Expression of col10a1, indian hedgehog, and patched was disrupted in mutants, reflecting improper chondrocyte/perichondrium signaling. Up-regulation of sox9a, sox9b, and runx2b in mutants suggested a molecular mechanism consistent with a role for proteoglycans in regulating skeletal cell fate. Together, our data reveal time-dependent changes to gene expression in uxs1 mutants that support a signaling role for proteoglycans during at least two distinct phases of skeletal development. These investigations are the first to examine the effect of mutation on the structure and function of Uxs1 protein in any vertebrate embryos, and reveal that Uxs1 activity is essential for the production and organization of skeletal extracellular matrix, with consequent effects on cartilage, perichondral, and bone morphogenesis.

Four loci differentially expressed in muscle tissue depending on water-holding capacity are associated with meat quality in commercial pig herds

Four genes, VTN, KERA, LYZ, and a non-annotated EST (Affymetrix probe set ID: Ssc.25503.1.S1_at), whose candidacy for traits related to water-holding capacity of meat arises from their trait-dependent differential expression, were selected for candidate gene analysis. Based on in silico analysis SNPs were detected, confirmed by sequencing and used to genotype animals of 4 pig populations including 3 commercial herds of Pietrain (PI), Pietrain x (German Large White x German Landrace) (PIF1), German Landrace (DL) and 1 experimental F2 population Duroc x Pietrain (DUPI). Comparative and genetic mapping established the location of VTN on SSC12, of LYZ and KERA on SSC5 and of UN on SSC7, coinciding with QTL regions for meat quality traits. VTN showed association with pH1, pH24 and drip loss. LYZ revealed association with conductivity 24, pH1 and drip loss. KERA was associated with pH. UN showed association with pH24 and drip loss, respectively. However, none of the candidate genes showed significant associations for a particular trait across all populations. This may be due to breed specific effects that are related to the differences in meat quality of theses pig breeds. The studies revealed statistic evidence for a link of genetic variation at these loci or close to them and promoted those four candidate genes as functional and/or positional candidate genes for meat quality traits.

MicroRNAs and micromanaging the skeleton in disease, development and evolution

MicroRNAs (miRNAs) are short, non-protein-encoding RNAs that effect post-transcriptional gene regulation by targeting messenger RNAs. miRNAs are associated with specific human diseases and help regulate development. Here we review recent advances in understanding the roles of miRNAs in skeletal malformations, including cleft palate, and in the evolution of skeletal morphologies. We propose the hypothesis that evolutionary variation in miRNA expression patterns or structural variation in miRNA binding sites in messenger RNAs can help explain the evolution of craniofacial variation among species, the development of human craniofacial disease and physiological changes leading to osteopenia that increases with ageing.

Bulldog dwarfism in Dexter cattle is caused by mutations in ACAN

Bulldog dwarfism in Dexter cattle is one of the earliest single-locus disorders described in animals. Affected fetuses display extreme disproportionate dwarfism, reflecting abnormal cartilage development (chondrodysplasia). Typically, they die around the seventh month of gestation, precipitating a natural abortion. Heterozygotes show a milder form of dwarfism, most noticeably having shorter legs. Homozygosity mapping in candidate regions in a small Dexter pedigree suggested aggrecan (ACAN) as the most likely candidate gene. Mutation screening revealed a 4-bp insertion in exon 11 (2266_2267insGGCA) (called BD1 for diagnostic testing) and a second, rarer transition in exon 1 (-198C>T) (called BD2) that cosegregate with the disorder. In chondrocytes from cattle heterozygous for the insertion, mutant mRNA is subject to nonsense-mediated decay, showing only 8% of normal expression. Genotyping in Dexter families throughout the world shows a one-to-one correspondence between genotype and phenotype at this locus. The heterozygous and homozygous-affected Dexter cattle could prove invaluable as a model for human disorders caused by mutations in ACAN.

Bone breaking strength and apparent metabolisability of calcium and phosphorus in selected and unselected broiler chicken genotypes

1. The present study examined the bone strength and apparent mineral metabolisability of a selected broiler chicken compared with those of a relatively unselected genotype. 2. Selected (SB) and unselected genotypes (UB) were reared under standard conditions and were fed on either a high quality (HQ) or a low quality (LQ) diet. Tibiotarsi samples were collected at 42 d from SB and compared to tibiotarsi from UB of the same age and the same body mass (BM). 3. Bones were assessed for: bone breaking strength (BBS), morphology (weight and length), and both organic (OM) and inorganic content (ASH). Apparent dry matter digestibility and the coefficient of apparent metabolisability of calcium and phosphorus were determined at the same BM. 4. The BBS of SB (214 +/- 9 N) was greater than that of same-age UB (119 +/- 8 N) but the same as that of same-BM UB (218 +/- 10 N). At the same age, the SB had stronger, heavier bones with more ash and organic matter per unit length of tibiotarsus than UB. At the same BM, the tibiotarsi of the SB were shorter and lighter, with a higher ash and a similar organic content than the bones of the UB. At the same BM, BBS was about 15% lower in both genotypes fed on the LQ compared to the HQ diet. 5. The coefficients of apparent metabolisability of calcium and phosphorus were the same in both genotypes when fed on the HQ diet, but were lower in the SB than in the UB genotype when the birds were given the LQ diet. 6. The tibiotarsi of the selected broilers were stronger, or at least as strong, as those of the unselected broiler genotype, which may be due to similar levels of apparent calcium metabolisability of the selected chickens.

Mutation analysis of the aggrecan gene in chickens with tibial dyschondroplasia

Expression studies suggest that the incidence and severity of tibial dyschondroplasia (TD) in chickens, Gallus gallus, may be affected by the aggrecan gene, AGC 1. Here, results are described of a scan for single nucleotide polymorphisms (SNP) in AGC1 in genetic lines divergently selected for TD incidence in chickens. A total of 3,048 bp of DNA sequence obtained from amplicons produced by 4 primer-pairs designed from the GenBank AGC1 cDNA sequence were scanned for SNP. Among the 18 SNP detected and validated, only 2 were nonsynonymous. Allelic frequency differences between TD-affected and nonaffected birds were not statistically significant for all the SNP. The current results do not support an association of Gallus gallus AGC1 variation at the DNA level with the incidence of TD in chickens. The genomic resources described, however, including the SNP, could be useful in further evaluating AGC1 in other populations for association with TD or other skeletal abnormalities.

The role of collagen in bone structure: An image processing approach

Bone collagen structure in normal and pathological tissues is illustrated using techniques of thin section transmission electron microscopy and computer-assisted analysis. The normal bone collagen types, fibril architecture and diameter are described. In pathological tissue, deviations from normal fine structure are reflected in abnormal arrangements of collagen fibrils and abnormalities in fibril diameter. Computer analyses of normal fibril positive staining patterns are presented in order to provide a basis for comparing such patterns with pathological ones.

An acute inflammatory response alters bone homeostasis, body composition, and the humoral immune response of broiler chickens

To quantify the effects of an acute phase response in broilers, chicks were injected with 1 mg/kg Escherichia coli lipopolysaccharide (LPS) at 15 and 23 d. Lipopolysaccharide injection increased feed/gain (P = 0.03), increased liver weight (P = 0.09), and decreased tibia calcium (P = 0.05) and breaking strength (P < 0.04) by d 28. In a second experiment, 3 d postinjection of chicks at d 31, LPS decreased BW (P < 0.01), breast weight (P = 0.08), and tibia breaking strength (P = 0.05), and increased liver weight (P < 0.01), mortality (P = 0.05), and titers to bronchitis and Mycoplasma gallisepticum that were induced by vaccination at hatch or by field exposure, respectively (P = 0.04). For experiment 3, chicks were challenged with LPS at 23d and 27d. Lipopolysaccharide-injected chicks had decreased BW (P = 0.06), feed consumption (P = 0.05), tibia weight (P< 0.01), and breaking strength (P < 0.01), and increased feed/gain (P < 0.01), liver weight (P < 0.01), and plasma ionized calcium level (P = 0.08). For experiment 4, chicks were injected with 0, 0.33, 0.66, 1.00, or 4.25 mg of LPS/kg of BW. There was an inverse relationship between LPS level and BW or bone breaking strength. Experiment 5 compared 4 broiler strains. Strain x LPS interactions were found for bone breaking strength (P = 0.01). Mortality before LPS challenge was inversely correlated to liver weight (r2 = 0.95, P = 0.02) and bone breaking strength (r2 = 0.99, P = 0.01) only after an LPS challenge.

Discondroplasia tibial: mecanismos de lesão e controle

A discondroplasia tibial (DT) é atribuída a uma assincronia no processo de diferenciação dos condrócitos, levando à formação de uma camada de condrócitos pré-hipertróficos e de uma cartilagem na tíbia proximal que não é calcificada, mas é resistente à invasão vascular. Além disso, tem sido proposto que, na discondroplasia tíbial, a etapa final do processo de calcificação não ocorre devido ao fato de que os efetores de alguns genes, relacionados com o mecanismo de calcificação do disco de crescimento podem apresentar algumas de suas propriedades químicas ou biológicas alteradas e/ou não serem expressos. Nesse sentido, a compreensão do mecanismo de ação e o papel das biomoléculas e dos minerais relacionados com a discondroplasia tibial poderão contribuir para o conhecimento de doenças do tecido ósseo e estabelecer estratégias de prevenção e tratamento.