Expression of genes involved in the somatotropic, thyrotropic, and corticotropic axes during development of Langshan and Arbor Acres chickens

In ovo injection of silver nanoparticles modulates some productive traits and hepatic gene expression of broilers exposed to lipopolysaccharide challenge

This study aimed to evaluate the effectiveness of the embryonic injection of silver nanoparticles (SilNPs) on some productive traits and hepatic gene expression of lipopolysaccharide (LPS)-challenged broilers after a 42 d rearing period. 560 fertile eggs were randomly allocated to four groups and received either of the following treatments at d 7 of incubation, control (no injection), placebo (1 mL saline), SilNP20 (20 mg/kg silver nanoparticles), or SilNP40 (40 mg/kg silver nanoparticles). After the incubation, 320 hatchlings experienced a 42 d standard rearing period. Live body weight (LBW), feed intake (FI), and feed conversion ratio (FCR) were weekly recorded. At the end of the experiment, two birds from each replicate (n = 8 per treatment) were exposed to LPS intraperitoneal injection at 48, 24, and 12 h before slaughter time. They were also used for blood, intestinal, and microbial evaluations. The hepatic mRNA levels of tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), transforming growth factor beta (TGF-β), and insulin-like growth factor I (IGF-I) were assessed at d 1 and 42 of the experiment. Adminstration of SiLNPs improved LBW, FI, and FCR and also enhanced liver and spleen weights (P < 0.05). SilNP20 birds had significantly lower bursa of Fabricius weight (P < 0.05). SilNP20 had lower total cholesterol levels than others. There was a significant difference (P < 0.05) between SliNP40 and SilNP20 in the ratio of villus height to crypt width. Compared to control groups, chicks of SilNP20, but not SilNP40, showed a significant increase in the relative expression of TNF-α, IL-6, TGF-β, and IFG-I genes at d 1. On d 42, however, both SilNP20 and SilNP40 had significantly higher TNF-α and TGF-β levels than both controls. Silver nanoparticles did not significantly affect the microflora of the ileum and cecum in the current study. In summary, SilNPs administration to chick embryos showed a long-term positive effect on their productive performance.

The Effect of Commercial Genetic Selection on Somatotropic Gene Expression in Broilers: A Potential Role for Insulin-Like Growth Factor Binding Proteins in Regulating Broiler Growth and Body Composition

The somatotropic axis influences growth and metabolism, and many of its effects are a result of insulin-like growth factor (IGF) signaling modulated by IGF-binding proteins (IGFBPs). Modern commercial meat-type (broiler) chickens exhibit rapid and efficient growth and muscle accretion resulting from decades of commercial genetic selection, and it is not known how alterations in the IGF system has contributed to these improvements. To determine the effect of commercial genetic selection on somatotropic axis activity, two experiments were conducted comparing legacy Athens Canadian Random Bred and modern Ross 308 male broiler lines, one between embryonic days 10 and 18 and the second between post-hatch days 10 and 40. Gene expression was evaluated in liver and breast muscle (pectoralis major) and circulating hormone concentrations were measured post-hatch. During embryogenesis, no differences in IGF expression were found that corresponded with difference in body weight between the lines beginning on embryonic day 14. While hepatic IGF expression and circulating IGF did not differ between the lines post-hatch, expression of both IGF1 and IGF2 mRNA was greater in breast muscle of modern broilers. Differential expression of select IGFBPs suggests their action is dependent on developmental stage and site of production. Hepatic IGFBP1 appears to promote embryonic growth but inhibit post-hatch growth at select ages. Results suggest that local IGFBP4 may prevent breast muscle growth during embryogenesis but promote it after hatch. Post-hatch, IGFBP2 produced in liver appears to inhibit body growth, but IGFBP2 produced locally in breast muscle facilitates development of this tissue. The opposite appears true for IGFBP3, which seems to promote overall body growth when produced in liver and restrict breast muscle growth when produced locally. Results presented here suggest that paracrine IGF signaling in breast muscle may contribute to overall growth and muscle accretion in chickens, and that this activity is regulated in developmentally distinct and tissue-specific contexts through combinatorial action of IGFBPs.

Profiles of expression pattern and tissue distribution of host defense peptides genes in different chicken (Gallus gallus) breeds related to body weight

Host defense peptides (HDPs) are an important first line of defense with antimicrobial and immunomodulatory properties. Selection for increased body weight is hypothesized to be related to reduced immune response. We studied the relationships among body weight, age, and the HDP expression patterns in intestine and immune organs. We used chickens with marked differences of body sizes. The non-selected Daweishan mini chickens showed the highest indexes of immune organs and the lowest concentrations of the plasma immune parameters C3, C4, IgA, and IgY, while the commercial Avian broiler showed the opposite results. The Daweishan mini chickens showed the highest mRNA expressions of HDP genes in small intestine followed by the semi-selected Wuding chickens. Compared with local breeds, broiler chickens showed higher mRNA expression of HDP genes in spleen, thymus, and bursa. Body weight and HDP expression levels were negatively correlated in the intestine and positively in the immune organs. Our results indicated that the HDP immune regulatory roles in small intestine acted as first line of defense in innate immunity in local breeds, and as an adaptive immunity in broiler chickens. Selection was associated with different expression expressions of HDP genes in breed-, age-, and organ-specific manners.

In ovo green light photostimulation during the late incubation stage affects somatotropic axis activity

Targeted green light photostimulation during the last stage of broiler incubation increases expression of the somatotropic axis. The purpose of this study was to further shorten the in ovo green light photostimulation and determine the critical age for photostimulation in broilers embryos, as a future strategy for broiler incubation. Fertile broilers eggs (n = 420) were divided into 5 treatment groups. The first group was incubated under standard conditions (in the dark) as the negative control group. The second was incubated under intermittent monochromatic green light using light-emitting diode lamps with an intensity of 0.1 W/m² at shell level from embryonic day (ED) 0 of incubation until hatch, as a positive control. The third, fourth, and fifth groups were incubated under intermittent monochromatic green light from ED 15, 16, and 18 of incubation, respectively, until hatch. All treatment groups showed elevated somatotropic axis expression compared with the negative control, with the group incubated under monochromatic green light from ED 18 until hatch showing results closest to the positive control. This suggests that broiler embryos can be exposed to in ovo green light photostimulation from a late stage of incubation (when transferring the eggs to the hatchery) and exhibit essentially the same outcome as obtained by photostimulation during the entire incubation period.

Comparative evaluation of growth performance, carcass characteristics and timed series gene expression profile of GH and IGF-1 in two Egyptian indigenous chicken breeds versus Rhode Island Red

Indigenous chicken breeds in developing countries have diverse benefits to rural economy as a source of high-quality animal protein. However, there are few reports on the evaluation of economic traits in Egyptian indigenous breeds. Hence, this study aimed to investigate growth performance, carcass characteristics, body measurements and meat quality traits in two indigenous breeds of chickens (Benha line and Golden Montazah) versus Rhode Island Red as a reference worldwide breed. Besides, a time series expression profile of somatotropic axis genes including GH and IGF-1 and their plasma level concentrations were investigated. Benha line chickens (BL) revealed the highest improved estimates of growth performance, carcass characteristics and meat quality traits. In the same manner, it displayed the highest levels of hepatic GH and IGF-1 and muscle IGF-1 gene expression compared to Rhode Island Red (RIR) and Golden Montazah (GM) chickens. Accordingly, BL exhibited the highest levels of plasma IGF-1 and the lowest levels of plasma GH. This result suggests the direct association between growth performance, carcass characteristics and levels of IGF-1 gene expression in the selected chicken breeds. BL is a superior Egyptian genotype with candidate productive traits and competing characteristics, it could be used widely as a proven ancestor of commercial hybrid breeds.

Melatonin Receptor Mel1b- and Mel1c-mediated Green Light Induced the Secretion of Growth Hormone in Anterior Pituitary of Chicks

Previous studies have found that melatonin was related to the growth and development in avian. Therefore, the newly hatched broilers were exposed to colors of light to establish a model of pinealectomy and explored the mechanism of pineal melatonin promoting growth hormone (GH) secretion. The results showed that green light (GL) promoted the levels of GH, pituitary-specific transcription factor-1 (Pit-1) genes and proteins in pituitary. Moreover, the mRNA and protein levels of melatonin receptor subtypes Mel1b and Mel1c in the pituitary in GL were higher than other monochromatic light groups. After pinealectomy, the expression of Pit-1, GH, Mel1b and Mel1c in pituitary decreased. In vitro, exogenous melatonin promoted the level of Pit-1 mRNA and the secretion of GH in anterior pituitary cells. However, when melatonin was added with exogenous selective Mel1b antagonist (4-phenyl-2-propionamideotetralin) and selective Mel1c antagonist (prazosin), the level of Pit-1 mRNA and the GH secretion decreased. When selective Mel1b and Mel1c antagonists were added simultaneously, the decrease in Pit-1 mRNA and GH secretion was more significant. These results indicated that pineal melatonin promotes the expression of Pit-1 under GL by binding to melatonin receptor subtypes Mel1b and Mel1c in the pituitary, thereby increasing GH secretion and promoting the growth.

In-ovo green light photostimulation during different embryonic stages affect somatotropic axis

Previous studies demonstrated that in-ovo photostimulation with monochromatic green light increased the somatotropic axis expression in broilers embryos. The objective of the current study was to detect the critical period for in-ovo GL photostimulation, in order to find the optimal targeted photostimulation period during the incubation process. Three hundred thirty-six fertile broiler eggs were divided into 4 groups. The first group was incubated under dark conditions as a negative control. The second incubated under intermittent monochromatic green light using light-emitting diode (LED) lamps with an intensity of 0.1 W\m2 at shell level from d 0 of the incubation as a positive control. The third group incubated under intermittent monochromatic green light from d 10 of the incubation. The last group incubated under intermittent monochromatic green light from d 15 of the incubation. In-ovo green light photostimulation from embryonic d 0 (ED0) increased plasma growth hormone (GH), as well as hypothalamic growth hormone releasing hormone (GHRH) and liver growth hormone receptor (GHR) and insulin-like growth factor-1 (IGF-1) mRNA levels. In-ovo green light photostimulation from ED10 increased the GH plasma levels compared to the negative control group, without affecting somatotropic axis mRNA genes expressions of GHRH, GHR, and IGF-1. In-ovo green light photostimulation from ED15 caused an increase in both the plasma GH levels and the somatotropic axis mRNA genes expressions of GHRH, GHR, and IGF-1, compared to the negative control group. These results suggest that the critical period of somatotropic axis acceleration by GL photostimulation start at 15 d of incubation.

Selection for growth rate and body size have altered the expression profiles of somatotropic axis genes in chickens

The growth hormone / insulin-like growth factor-1 (GH/IGF-1) pathway of the somatotropic axis is the major controller for growth rate and body size in vertebrates, but the effect of selection on the expression of GH/IGF-1 somatotropic axis genes and their association with body size and growth performance in farm animals is not fully understood. We analyzed a time series of expression profiles of GH/IGF-1 somatotropic axis genes in two chicken breeds, the Daweishan mini chickens and Wuding chickens, and the commercial Avian broilers hybrid exhibiting markedly different body sizes and growth rates. We found that growth rate and feed conversion efficiency in Daweishan mini chickens were significantly lower than those in Wuding chickens and Avian broilers. The Wuding and Daweishan mini chickens showed higher levels of plasma GH, pituitary GH mRNA but lower levels of hepatic growth hormone receptor (GHR) mRNA than in Avian broilers. Daweishan mini chickens showed significantly lower levels of plasma IGF-1, thigh muscle and hepatic IGF-1 mRNA than did Avian broilers and Wuding chickens. These results suggest that the GH part of the somatotropic axis is the main regulator of growth rate, while IGF-1 may regulate both growth rate and body weight. Selection for growth performance and body size have altered the expression profiles of somatotropic axis genes in a breed-, age-, and tissue-specific manner, and manner, and alteration of regulatory mechanisms of these genes might play an important role in the developmental characteristics of chickens.

Transcriptomic profile of leg muscle during early growth in chicken

The early growth pattern, especially the age of peak growth, of broilers affects the time to market and slaughter weight, which in turn affect the profitability of the poultry industry. However, the underlying mechanisms regulating chicken growth and development have rarely been studied. This study aimed to identify candidate genes involved in chicken growth and investigated the potential regulatory mechanisms of early growth in chicken. RNA sequencing was applied to compare the transcriptomes of chicken muscle tissues at three developmental stages during early growth. In total, 978 differentially expressed genes (DEGs) (fold change ≥ 2; false discovery rate < 0.05) were detected by pairwise comparison. Functional analysis showed that the DEGs are mainly involved in the processes of cell growth, muscle development, and cellular activities (such as junction, migration, assembly, differentiation, and proliferation). Many of the DEGs are well known to be related to chicken growth, such as MYOD1, GH, IGF2BP2, IGFBP3, SMYD1, CEBPB, FGF2, and IGFBP5. KEGG pathway analysis identified that the DEGs were significantly enriched in five pathways (P < 0.1) related to growth and development: extracellular matrix–receptor interaction, focal adhesion, tight junction, insulin signaling pathway, and regulation of the actin cytoskeleton. A total of 42 DEGs assigned to these pathways are potential candidate genes inducing the difference in growth among the three developmental stages, such as MYH10, FGF2, FGF16, FN1, CFL2, MAPK9, IRS1, PHKA1, PHKB, and PHKG1. Thus, our study identified a series of genes and several pathways that may participate in the regulation of early growth in chicken. These results should serve as an important resource revealing the molecular basis of chicken growth and development.

Corticotropin-releasing hormone: Mediator of vertebrate life stage transitions?

Hormones, particularly thyroid hormones and corticosteroids, play critical roles in vertebrate life stage transitions such as amphibian metamorphosis, hatching in precocial birds, and smoltification in salmonids. Since they synergistically regulate several metabolic and developmental processes that accompany vertebrate life stage transitions, the existence of extensive cross-communication between the adrenal/interrenal and thyroidal axes is not surprising. Synergies of corticosteroids and thyroid hormones are based on effects at the level of tissue hormone sensitivity and gene regulation. In addition, in representative nonmammalian vertebrates, corticotropin-releasing hormone (CRH) stimulates hypophyseal thyrotropin secretion, and thus functions as a common regulator of both the adrenal/interrenal and thyroidal axes to release corticosteroids and thyroid hormones. The dual function of CRH has been speculated to control or affect the timing of vertebrate life history transitions across taxa. After a brief overview of recent insights in the molecular mechanisms behind the synergic actions of thyroid hormones and corticosteroids during life stage transitions, this review examines the evidence for a possible role of CRH in controlling vertebrate life stage transitions.

Mechanisms involved in glucocorticoid induction of pituitary GH expression during embryonic development

Glucocorticoid hormones are involved in functional differentiation of GH-producing somatotrophs. Glucocorticoid treatment prematurely induces GH expression in mammals and birds in a process requiring protein synthesis and Rat sarcoma (Ras) signaling. The objective of this study was to investigate mechanisms through which glucocorticoids initiate GH expression during embryogenesis, taking advantage of the unique properties of chicken embryos as a developmental model. We determined that stimulation of GH expression occurred through transcriptional activation of GH, rather than enhancement of mRNA stability, and this process requires histone deacetylase activity. Through pharmacological inhibition, we identified the ERK1/2 pathway as a likely downstream Ras effector necessary for glucocorticoid stimulation of GH. However, we also found that chronic activation of ERK1/2 activity with a constitutively active mutant or stimulatory ligand reduced initiation of GH expression by glucocorticoid treatment. Corticosterone treatment of cultured embryonic pituitary cells increased ERK1/2 activity in an apparent cyclical manner, with a rapid increase within 5 minutes, followed by a reduction to near-basal levels at 3 hours, and a subsequent increase again at 6 hours. Therefore, we conclude that ERK1/2 signaling must be strictly controlled for maximal glucocorticoid induction of GH to occur. These results are the first in any species to demonstrate that Ras- and ERK1/2-mediated transcriptional events requiring histone deacetylase activity are involved in glucocorticoid induction of pituitary GH during embryonic development. This report increases our understanding of the molecular mechanisms underlying glucocorticoid recruitment of somatotrophs during embryogenesis and should provide insight into glucocorticoid-induced developmental changes in other tissues and cell types.

Expression Profiles of the Insulin-like Growth Factor System Components in Liver Tissue during Embryonic and Postnatal Growth of Erhualian and Yorkshire Reciprocal Cross F1 Pigs

In Erhualian and Yorkshire reciprocal cross F1 pig populations, we examined the mRNA expression characteristic of liver-derived IGF-1, IGF-1R, IGF-2, IGF-2R and IGFBP-3 during the embryonic and postnatal developmental periods (E50, E70, E90, D1, D20, D70, D120 and D180). Our results demonstrated that the IGF-system genes mRNA levels exhibited an ontogenetic expression pattern, which was potentially associated with the porcine embryonic development, postnatal growth, organogenesis and even the initiation and acceleration of puberty. The expression pattern of IGF-system genes showed variation in the reciprocal cross (F1 YE and EY pigs). This study also involved the expression features of imprinted genes IGF-2 and IGF-2R. The parent-of-origin effect of imprinted genes was reflected by their differential expression between the reciprocal crosses populations. The correlation analysis also indicated that the regulatory network and mechanisms involved in the IGF system were a complex issue that needs to be more fully explored. A better understanding of IGF system components and their interactive mechanisms will enable researchers to gain insights not only into animal organogenesis but also into somatic growth development and even reproduction.

Hatching the cleidoic egg: the role of thyroid hormones

A major life stage transition in birds and other oviparous sauropsids is the hatching of the cleidoic egg. Not unlike amphibian metamorphosis, hatching in these species can be regarded as a transition from a relatively well-protected "aqueous" environment to a more hazardous and terrestrial life outside the egg, a transition in which thyroid hormones (THs) (often in concert with glucocorticoids) play an important role. In precocial birds such as the chicken, the perihatch period is characterized by peak values of THs. THs are implicated in the control of muscle development, lung maturation and the switch from chorioallantoic to pulmonary respiration, yolk sac retraction, gut development and induction of hepatic genes to accommodate the change in dietary energy source, initiation of thermoregulation, and the final stages of brain maturation as well as early post-hatch imprinting behavior. There is evidence that, at least for some of these processes, THs may have similar roles in non-avian sauropsids. In altricial birds such as passerines on the other hand, THs do not rise significantly until well after hatching and peak values coincide with the development of endothermy. It is not known how hatching-associated processes are regulated by hormones in these animals or how this developmental mode evolved from TH-dependent precocial hatching.

Ontogeny of mRNA expression of somatostatin and its receptors in chicken embryos in association with methylation status of their promoters

The present study was designed to investigate the ontogeny and tissue distribution of somatostatin and its five receptor subtypes (SSTR1-5) mRNA expression in embryonic chicken (Gallus gallus). Brain, gonads (male), intestine, kidney, liver, muscle, stomach and yolk sac membrane (YSM) of chicken embryos on the embryonic (E) ages of 10, 16 and 21days (right before hatch) were investigated. Bisulfite sequencing PCR (BSP) was performed to determine the methylation status of the promoter region of all the six genes in the liver. Somatostatin (SST) was predominately expressed in intestine, brain and gonads (male) with different ontogenic patterns. The highest expression in intestine was detected at E10. There was ontogenic shift from intestine to brain as development progressed. Expression pattern of SSTRs in brain, intestine and kidney was similar to human embryonic expression. In liver, the ontogenic expression pattern of SST and its receptors was associated to methylation status of the respective promoters. Methylation of site Sp1 determines expression level of SST, SSTR1, SSTR2 and SSTR3 while site a is important in governing the expression of SSTR4 and SSTR5. The results show that ontogenic expression profile of chicken SST and SSTRs is time and tissue specific.

Developmental transcription of genes putatively associated with growth in two sturgeon species of different growth rate

In the present study, we surveyed developmental changes in the transcription of growth hormone (gh), insulin-like growth factor-I (igf-I), ghrelin (ghrl) and vascular endothelial growth factor (vegf) genes in the largest freshwater fish, European sturgeon (Beluga, Huso huso) and compared the same parameters to that of its phylogenically close moderate-sized species, Persian sturgeon (Acipenser persicus). The transcripts of gh, igf-I, ghrl and vegf were detected at all developmental time-points of Persian sturgeon and Beluga from embryos to juvenile fish. Changes in normalized gh, igf-I, ghrl and vegf transcription by using the geometric average of genes encoding ribosomal protein L6 (RPL6) and elongation factor (EF1A) over the time of development of Persian sturgeon and Beluga were statistically significant (P<0.05). Our results showed that the mRNA expression levels of both igf-I and ghrl were low during early larval development and then increased significantly to the late larval time-points when larvae started exogenous feeding. In both Beluga and Persian sturgeon, after a low mRNA expression during the embryonic stage, the transcript levels of vegf displayed an increasing trend during yolk-sac fry, consistent with organogenesis. The vegf level remained constantly high in the time of exogenous feeding. The highest detection of gh transcripts coincided with the end of the embryonic stage (hatching time) in Persian sturgeon and 3 days-post-hatching (dph) in Beluga. In Persian sturgeon, the gh transcript started to decrease to the rest of the developmental time-points, whereas in Beluga gh transcript had a marked second increase from the time of exogenous feeding (20-dph). This Beluga specific increase in gh transcription may be associated with the marked growth rate and extraordinary size of this fish species.

Recent advances in the phylogenetic study of ghrelin

To understand fully the biology of ghrelin, it is important to know the evolutionary history of ghrelin and its receptor. Phylogenetic and comparative genomic studies of mammalian and non-mammalian vertebrates are a useful approach to that end. Ghrelin is a hormone that has apparently evaded natural selection during a long evolutionary history. Surely ghrelin plays crucial physiological roles in living animals. Phylogenetic studies reveal the nature and evolutionary history of this important signaling system.

Expression of the insulin-like growth factor system in skeletal muscle during embryonic and postnatal development in the first filial generation pigs from Erhualian and Yorkshire reciprocal crosses

In this study, we detected the expression of IGF-I, IGF-II, IGF-IR, IGF-IIR, and IGFBP-3 mRNA at 50 (E50), 70 (E70), and 90 (E90) days of gestation, and 1 (D1), 20 (D20), 70 (D70), 120 (D120), and 180 (D180) days of age in the longissimus dorsi (LD) and the semitendinosus (ST) of pigs from a Yorkshire boar×Erhualian sow (YE) cross as well as a Erhualian boar×Yorkshire sow (EY) cross. We found that the expression of IGF-I and IGF-II mRNA in skeletal muscle tissues differed based on developmental age and reciprocal cross type (P<0.05). The expression of IGF-I mRNA exhibited a fluctuant ascending trend. In contrast, IGF-II showed a fluctuant descending trend after birth. The levels of IGF-IR mRNA were higher before birth compared with after birth except for the ST of EY pigs at D120 (P<0.05). The expression of IGF-IIR and IGFBP-3 mRNA remarkably changed with age and reciprocal cross type (P<0.05). IGF-I, IGF-II, and IGFBP-3 mRNA were positively correlated with IGF-IR from 50E to 180D. These data suggest that the expression of IGF-system genes exhibits specific developmental patterns in the skeletal muscle tissues of pigs from reciprocal crosses at different developmental stages and may show linked expression during certain periods of development. Our results may provide a valuable resource for the molecular breeding of pigs.

Ontogenic characterization of gene expression in the developing neuroendocrine system of the chick

The neuroendocrine system consists of five major hypothalamic-pituitary hormone axes that regulate several important metabolic processes, and it develops in all vertebrates during embryogenesis. In order to define initiation and establishment of these five axes, mRNA expression profiles of hypothalamic releasing and release-inhibiting factors, their pituitary receptors, and pituitary hormones were characterized during the second half of embryogenesis and first week post-hatch in the chick. Axis initiation was defined as the age when pituitary hormone mRNA levels began to increase substantially, and establishment was defined as the age when mRNA for all components had reached maximum expression levels. The adrenocorticotropic axis appears established by e12, as there were no major increases in gene expression after that age. Hypothalamic thyrotropin-releasing hormone and pituitary thyroid-stimulating hormone β-subunit increased between e10 and e18, indicating establishment of the thyrotropic axis during this period. Pituitary growth hormone substantially increased on e16, and hypothalamic growth hormone-releasing hormone did not increase until e20, indicating that somatotropic axis activity is established late in embryonic development. Lactotropic axis initiation is evident just prior to hatch, as pituitary prolactin and vasoactive intestinal peptide receptor 1 did not increase until e18 and e20, respectively. Hypothalamic gonadotropin-releasing hormone 1 increased after hatch, and pituitary luteinizing hormone β-subunit expression remained low until d3, indicating the gonadotropic axis is not fully functional until after hatching. This study is the first to characterize major hypothalamic and pituitary components of all five neuroendocrine axes simultaneously and considerably increases our understanding of neuroendocrine system establishment during development.

Role of the insulin-like growth factor system in epiphyseal cartilage on the development of Langshan and Arbor Acres chickens, Gallus domesticus

We measured the mRNA transcript expression patterns for members of the insulin-like growth factor (IGF) system during embryonic and postnatal development in epiphyseal cartilage from Langshan (LS) and Arbor Acres (AA) chickens. Insulin-like growth factor binding protein (IGFBP)-2 expression was positively correlated with IGF-I from embryonic day (E) 14 to postnatal d (P) 0 and with IGF-II from E14 to P14 but negatively correlated with IGF-I from P0 to P42 and IGF-II from P14 to P42. Expression of IGFBP-5 correlated positively with IGF-I from E14 to P0 but negatively from P0 to P28. The results suggest that these genes are regulated in a coordinated fashion during development. A negative correlation was found between IGFBP-7 and IGF-II during P0 to P42. A positive correlation was found between IGFBP-3 (E14 to E18, P14 to P42) and IGF-IR and between IGFBP-3 (E14 to P0, P14 to P42) and IGF-I. The endocrine factors can be integrated with nutrition to regulate animal growth. In our study, AA chickens were fed a nutrient-rich AA diet, and LS chickens were fed either an AA diet or a less-rich diet. The LS and AA chickens fed the same AA diet showed no differences in IGF-I, IGF-I receptor, IGFBP-2, IGFBP-5, IGFBP-7, and IGFBP-3 but did still show differences in IGF-II. Our data indicate that these select genes may show linked expression during certain periods of development and that differences in gene expression respond differently to nutrient intake in LS and AA chickens.