Stages Of Postnatal Development Research Articles

The role of the Shh signaling pathway in radio‐induced cataractogenesis

SummaryBesides the well‐known role in cancer, Shh signaling pathway direct cell proliferation, cell fate determination and EMT, remaining largely expressed in the stem cell compartment of adult tissues. Recently, we proposed Ptch1+/‐ mice as a relevant radiation‐induced cataract mouse model. These mice, develop cataract with a very high incidence (45.2%) and short latency after irradiation with 3 Gy of x‐rays, when radiation is delivered during the early stage of postnatal lens development. Molecular analyses suggest that Shh and TGF‐ß signaling cooperate to promote Ptch1‐associated cataract development by activating EMT and converging on Nanog. Furthermore, using a range of decreasing radiation doses to assess the cataract response in these mice, nonlinear biological responses were observed using doses ≤ 1 Gy, with a suggestion for borderline effects at 2 Gy, both for gross cataract development and for activation of the genetic pathways involved in the molecular pathogenesis of Shh‐associated cataract.These findings highlight a novel function of Shh signaling unrelated to cancer and provide a new animal model to investigate the molecular pathogenesis of cataract formation.

Telocytes play a key role in prostate tissue organisation during the gland morphogenesis.

Telocytes are CD34‐positive interstitial cells, known to exert several functions, one of which is a role in tissue organisation, previously demonstrated by telocytes in the myocardium. The existence of telocytes in the prostate has recently been reported, however, there is a lack of information regarding the function of these cells in prostate tissue, and information regarding the possible role of these cells in prostatic development. This study used immunofluorescence techniques in prostate tissue and prostatic telocytes in culture to determine the relationship between telocytes and prostate morphogenesis. Furthermore, immunofluorescent labelling of telocytes was performed on prostate tissue at different stages of early postnatal development. Initially, CD34‐positive cells are found at the periphery of the developing alveoli, later in the same region, c‐kit‐positive cells and cells positive for both factors are verified and CD34‐positive cells were predominantly observed in the interalveolar stroma and the region surrounding the periductal smooth muscle. Fluorescence assays also demonstrated that telocytes secrete TGF‐β1 and are ER‐Beta (ERβ) positive. The results suggest that telocytes play a changing role during development, initially supporting the differentiation of periductal and perialveolar smooth muscle, and later, producing dense networks that separate alveoli groups and form a barrier between the interalveolar region and periurethral smooth muscle. We conclude that telocytes play a relevant role in prostate tissue organisation during postnatal development.

Oxidative and glycolytic skeletal muscles show marked differences in gene expression profile in Chinese Qingyuan partridge chickens.

Oxidative and glycolytic myofibers have different structures and metabolic characteristics and their ratios are important in determining poultry meat quality. However, the molecular mechanisms underlying their differences are unclear. In this study, global gene expression profiling was conducted in oxidative skeletal muscle (obtained from the soleus, or SOL) and glycolytic skeletal muscle (obtained from the extensor digitorum longus, or EDL) of Chinese Qingyuan partridge chickens, using the Agilent Chicken Gene Expression Chip. A total of 1224 genes with at least 2-fold differences were identified (P < 0.05), of which 654 were upregulated and 570 were downregulated in SOL. GO, KEGG pathway, and co-expressed gene network analyses suggested that PRKAG3, ATP2A2, and PPARGC1A might play important roles in myofiber composition. The function of PPARGC1A gene was further validated. PPARGC1A mRNA expression levels were higher in SOL than in EDL muscles throughout the early postnatal development stages. In myoblast cells, shRNA knockdown of PPARGC1A significantly inhibited some muscle development and transition-related genes, including PPP3CA, MEF2C, and SM (P < 0.01 or P < 0.05), and significantly upregulated the expression of FWM (P < 0.05). Our study demonstrates strong transcriptome differences between oxidative and glycolytic myofibers, and the results suggest that PPARGC1A is a key gene involved in chicken myofiber composition and transition.

Androgen receptor is expressed in mouse cardiomyocytes at prenatal and early postnatal developmental stages

BackgroundPrevious studies show that androgens are involved in hypertrophy and excitability of cardiomyocytes and that their effects are mediated through their receptor. The aim of this study was to evaluate the presence of androgen receptor (AR) in mouse heart during prenatal and early postnatal stages.ResultsThe expression of AR and related genes, alpha myosin heavy chain -Myh6-, beta myosin heavy chain -Myh7- and atrial natriuretic factor –Nppa- was simultaneously evaluated by semiquantitative RT-PCR. AR was also detected by immunohistochemistry. Androgen receptor mRNA was detected in hearts from 10.5 days post coitum to 16 postnatal days. A higher expression of AR mRNA in atria compared to ventricles was observed in neonatal mouse. A positive correlation between mRNA levels of AR and Nppa was observed in mouse heart at early postnatal development. Androgen receptor expression is similar in males and females during cardiac development. Finally, androgen receptor protein was observed by immunohistochemistry in myocardial cells of atria and ventricles from 12.5 days onwards and restricted after 16.5 days post-coitum to nuclei of cardiomyocytes.ConclusionPresent results provide evidence that androgen receptor is expressed from prenatal stages in mouse heart, supporting the proposition that androgens could be involved in mammalian heart development.

Reduced protein expressions of cytomembrane GABAARβ3 at different postnatal developmental stages of rats exposed prenatally to valproic acid

Decreased inhibition plays an extremely important role in pathogenesis of autism spectrum disorder (ASD). Therefore, we aimed to determine whether expression levels of the γ-aminobutyric acid type A receptor β3 subunit (GABAARβ3), K+-Cl− cotransporter 2 (KCC2), and Na+-K+-Cl− cotransporter 1 (NKCC1) related to inhibition transmission are changed in a sodium valproate-induced rat model of ASD. Decreased expression levels of membrane GABAARβ3 (m-GABAARβ3) and KCC2 as well as increased endocytosis of GABAARs were found in the model group. However, there were no significant differences in expression of total GABAARβ3 and NKCC1 between the control and model groups. In addition, we observed growth retardation, impaired spatial memory, limited exploration, increased anxiety, and reduced sociability in the model group. These results suggest alterations in m-GABAARβ3 levels, KCC2 levels, and trafficking of GABAARs in rats prenatally exposed to valproic acid and advance our understanding of the pathogenesis of ASD.

Відмінності вмісту металотіонеїну у мозку гризунів за умов постнатального розвитку та кадмієвої інтоксикації

Introduction. Metal-binding metallothionein genes are found in a vast population of organisms. These proteins are non enzymatic and very rich in cysteine residues. The various metallothionein isoforms in different brain regions arguably change over time.The aim of the study – evaluating the distribution of metallothionein in different brain regions of gerbils and Wistar rats at different stages of postnatal development (PND), under standard and low dose Cd-induced conditions.Materials and Methods. 18 Mongolian gerbils and 36 Wistar rats were divided into 6 groups (n=6), by age and condition of experiment: groups 1, 2, 3, 4 – 1, 30, 90 and 180-days old were exposed to standard conditions; group 5 and 6 – 180-days old+0.1 or 1.0 µgµg Cd2+ per animal everyday for 36 days. The metallothionein content in the hippocampus, cerebellum, and thalamus were detected by the ELISA.Results and Discussion. Obtained data was shown the dynamic of metallothionein distribution in different brain regions of gerbils and Wistar rats depending on the stage of postnatal development and functional capacities. The content of metallothionein in the hippocampus continually decreased in both animal types but the cerebella metallothionein distribution pattern was different from that of the hippocampus, but identical in both rodents, rising from day one before decreasing on day 30. The low levels of metallothionein under the influence of Cd were proportional to the doses administered.Conclusions. The level of metallothionein in the brain varies depending on the stage of development of the functional capacities of the brain parts. The significant down-regulation of metallothionein in the investigated brain regions under Cd influence suggests that a decrease in metallothionein levels depends on the dose of Cd and on the time necessary for its accumulation.

Postnatal developmental of Neuromedin S and its receptor in the male Xiaomeishan pig reproductive axis

Neuromedin S (NMS) has been identified as an endogenous ligand for FM-3/GPR66 and FM-4/TGR-1 which are NMU receptors NMUR1 and NMUR2, respectively. The NMS molecule is present in some peripheral tissues and the central nervous system (CNS), and it had been documented that NMS has fundamental and important roles in multiple physiological functions and processes such as circadian rhythm, energy balance, feeding behavior, stress responses and reproduction. The possible role of NMS in sexual development postnatally, however, is still obscure. This study aims to determine the change of NMS and its receptor gene expression in the reproductive axis of male Xiaomeishan pigs, postnatally. Firstly, the cDNA of the NMS and its receptors was cloned and sequenced. The results showed that there was a lack of 12 amino acids in the C-terminal of the male Xiaomeishan pig NMS amino-acid sequences compared with other animal species, but the main protein structure of prepro-NMS was high in homology. In addition, the nucleotide sequence and amino acids of the male Xiaomeishan pig’s NMUR1 and NMUR2 had high homology. The NMS and NMUR2 mRNA in the male Xiaomeishan pig was detected in the reproductive axis at postnatal development stages, including postnatal day 3, 30, 60, 90 and 120, using real-time PCR and immunohistochemistry. The data showed that there were developmental changes in NMS and NMUR2 in the reproductive axis of the male Xiaomeishan pigs, postnatally, which suggested that NMS and NMUR2 might have a role in the development of the boar reproductive axis, but its regulatory mechanism remains to be elucidated.

Pre- and postnatal psychosocial intervention concepts

Psychiatry, psychoanalysis and infant mental health research of the last decades have led to intervention concepts for pre- and postnatal stages of human development. Such concepts reach from how parents-to-be can be prepared for parenthood to how to intervene in support of relation and attachment in infants, toddlers and older children. Especially the postnatal relation of infant and parents has been examined extensively, as have parental competencies. The expression of intuitive parental competencies (according to Papousek and Papousek) may be compromised by diverse factors, thus putting the infant's psychic development at risk in general. Early intervention concepts may help out to some extent. In German-speaking countries, there are intervention programs focusing on bonding as there are on handling, processing of and coping with trauma, on promoting secure attachment between infant and parents, on relational issues, on bodily contact, on understanding the infant's signals, including those of the preterm infant, as well as on educational practices. From prenatal period onwards up to kindergarten age there are structured interventions, including the involvement of parents and parents-to-be. Yet, some factors of psychic development and of pathology may not necessarily be reached by these. Whereas concepts on an individual level of personality education do exist, nevertheless there might have to be collective measures. There seems to be a need to augment the agenda as there is good reason to assume that in the last decades there has been a motion toward new social deprivation stemming from societal depravation processes, which might potentiate future deprivation.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Age-related Microscopic Changes in the Thyroid Gland of West African Dwarf Goat During Foetal and Post-natal Periods of Development

The histometric and histologic standard techniques were used to provide comprehensive information on the morphological changes in the thyroid gland of West African Dwarf goat during the foetal and postnatal development stages. The foetal age was determined using crown rump length and the pre-pubertal and pubertal age of animals was determined by dentition. The early foetal thyroid, surrounded by a thin capsule of dense irregular connective tissue, was continuous with well vascularised loose connective tissue septa. The parenchyma was composed of solid cell clusters of follicular epithelial cells surrounding small lumina. Follicular arrangement was indistinct in foetal thyroid by 50-70 days of gestational age and many follicles of different sizes were present by 95-125 days onwards. Significant variations in the mean follicular diameter, mean capsule thickness and mean epithelial cell height of the thyroids were observed in all stages of development. The mean large follicular diameter in the foetal, pre-pubertal and pubertal ages were 17.70 ± 0.09 µm, 54.41 ± 0.28 µm,142.77 ± 0.51 µm respectively. The follicular cells were of low cuboidal shape in foetuses, assumed high cuboidal or columnar form in pre-pubertal group and squamous in older pubertal age. Ultimobranchial follicles were encountered in early foetal goat thyroids, while focal areas of follicular cell hyperplasia were frequently seen in the older pubertal thyroids. The strong PAS-positive reaction increased strikingly from the 95-125 days foetal age, and by pubertal age all follicles were fully distended with colloid. Colloid vacuolation (colloid droplets) were encountered frequently by the age of 95-125 days, indicating the ability to synthesize hormones towards the last trimester of gestation. Parafollicular cells were distinguished by its pale cytoplasm and large nucleus at 75-90 days onwards. They were located basally and as clusters in the interfollicular tissue. This finding suggested possible high prenatal function for the thyroids of goats in the synthesis of thyroid hormones.

Deficient Circumferential Growth Is the Primary Determinant of Aortic Obstruction Attributable to Partial Elastin Deficiency.

Williams syndrome is characterized by obstructive aortopathy attributable to heterozygous loss of ELN, the gene encoding elastin. Lesions are thought to result primarily from excessive smooth muscle cell (SMC) proliferation and consequent medial expansion, although an initially smaller caliber and increased stiffness of the aorta may contribute to luminal narrowing. The relative contributions of such abnormalities to the obstructive phenotype had not been defined. We quantified determinants of luminal stenosis in thoracic aortas of Eln-/- mice incompletely rescued by human ELN. Moderate obstruction was largely because of deficient circumferential growth, most prominently of ascending segments, despite increased axial growth. Medial thickening was evident in these smaller diameter elastin-deficient aortas, with medial area similar to that of larger diameter control aortas. There was no difference in cross-sectional SMC number between mutant and wild-type genotypes at multiple stages of postnatal development. Decreased elastin content was associated with medial fibrosis and reduced aortic distensibility because of increased structural stiffness but preserved material stiffness. Elastin-deficient SMCs exhibited greater contractile-to-proliferative phenotypic modulation in vitro than in vivo. We confirmed increased medial collagen without evidence of increased medial area or SMC number in a small ascending aorta with thickened media of a Williams syndrome subject. Deficient circumferential growth is the predominant mechanism for moderate obstructive aortic disease resulting from partial elastin deficiency. Our findings suggest that diverse aortic manifestations in Williams syndrome result from graded elastin content, and SMC hyperplasia causing medial expansion requires additional elastin loss superimposed on ELN haploinsufficiency.

Prospects and limitations of improving skeletal growth in a mouse model of spondyloepiphyseal dysplasia caused by R992C (p.R1192C) substitution in collagen II.

Skeletal dysplasias form a group of skeletal disorders caused by mutations in macromolecules of cartilage and bone. The severity of skeletal dysplasias ranges from precocious arthropathy to perinatal lethality. Although the pathomechanisms of these disorders are generally well defined, the feasibility of repairing established aberrant skeletal tissues that developed in the presence of mutant molecules is currently unknown. Here, we employed a validated mouse model of spondyloepiphyseal dysplasia (SED) that enables temporal control of the production of the R992C (p.R1192C) collagen II mutant that causes this disease. Although in our earlier studies we determined that blocking the expression of this mutant at the early prenatal stages prevents a SED phenotype, the utility of blocking the R992C collagen II at the postnatal stages is not known. Here, by switching off the expression of R992C collagen II at various postnatal stages of skeletal development, we determined that significant improvements of cartilage and bone morphology were achieved only when blocking the production of the mutant molecules was initiated in newborn mice. Our study indicates that future therapies of skeletal dysplasias may require defining a specific time window when interventions should be applied to be successful.

Diminished satellite cell fusion and S6K1 expression in myotubes derived from skeletal muscle of low birth weight neonatal pigs.

Low birth weight (LBWT) is consistently associated with impaired postnatal muscle growth in mammals. Satellite cell (SC)‐mediated myonuclear incorporation precedes protein accumulation in the early stages of postnatal muscle development and growth. The objective of this study was to investigate proliferation and differentiation of SCs and the regulation of protein synthesis signaling in response to insulin‐like growth factor (IGF)‐I stimulation in SC‐derived myotubes of LBWT neonatal pigs. SCs isolated from Longissimus dorsi muscle of LBWT and NBWT pigs (3‐d‐old, n = 8) were cultured and induced to proliferate and differentiate to myotubes in vitro. On day 3 of differentiation, myotubes were fasted in serum‐free media for 3 h and treated with human recombinant R3‐insulin‐like growth factor‐I (rh IGF‐I) at 0, 25, and 50 ng × mL−1 for 30 min. There was no difference in proliferation rates of SCs from LBWT and NBWT pigs. However, LBWT SC fusion was 15% lower (P ≤ 0.05) without a difference in MyoD or myogenin mRNA expression in comparison with NBWT pigs, suggesting SCs are not intrinsically different between the two groups. IGF‐Ι stimulation at physiological concentrations activated downstream effectors of mTOR similarly in myotubes from LBWT and NBWT pigs. However, abundance of ribosomal protein S6 kinase 1(S6K1) was lower in myotubes of LBWT compared to their NBWT siblings (P ≤ 0.05). These results indicate that the modest reduction in SC fusion and S6K1 expression are not the major contributors to the impaired postnatal muscle growth of LBWT pigs.

Over-expression of myosin7A in cochlear hair cells of circling mice

Circling mouse (C57BL/6J-cir/cir) deleted the transmembrane inner ear (Tmie) gene is an animal model for human non-syndromic recessive deafness, DFNB6. In circling mouse, hair cells in the cochlea have degenerated and hair bundles have become irregularity as time goes on. Tmie protein carries out a function of the mechanoelectrical transduction channel in cochlear hair cells. Myosin7a (MYO7A) protein has key roles in development of the cochlear hair bundles as well as in the function of cochlear hair cells. To find whether Tmie protein interacts with MYO7A proteins in the cochlea postnatal developmental stage, we investigated expression of the MYO7A proteins in the cochlear hair cells of circling mice by western blot analysis and whole mount immunofluorescence at postnatal day 5 (P5). The expression of MYO7A showed statistically significant increase in the cochlea of C57BL/6J-+/cir and C57BL/6J-cir/cir mice than that of C57BL/6J-+/+ mice. The MYO7A intensity of the cochlear hair cells also increased in C57BL/6J-+/cir and C57BL/6J-cir/cir mice compared with those of C57BL/6J-+/+ mice. Taken together, the results indicate that Tmie protein may have an important role with MYO7A protein in the development and maintenance of the stereociliary bundles during postnatal developmental stage of the cochlea.

PEDF Is Associated with the Termination of Chondrocyte Phenotype and Catabolism of Cartilage Tissue

Objective. To investigate the expression and target genes of pigment epithelium-derived factor (PEDF) in cartilage and chondrocytes, respectively. Methods. We analyzed the expression pattern of PEDF in different human cartilaginous tissues including articular cartilage, osteophytic cartilage, and fetal epiphyseal and growth plate cartilage, by immunohistochemistry and quantitative real-time (qRT) PCR. Transcriptome analysis after stimulation of human articular chondrocytes with rhPEDF was performed by RNA sequencing (RNA-Seq) and confirmed by qRT-PCR. Results. Immunohistochemically, PEDF could be detected in transient cartilaginous tissue that is prone to undergo endochondral ossification, including epiphyseal cartilage, growth plate cartilage, and osteophytic cartilage. In contrast, PEDF was hardly detected in healthy articular cartilage and in the superficial zone of epiphyses, regions that are characterized by a permanent stable chondrocyte phenotype. RNA-Seq analysis and qRT-PCR demonstrated that rhPEDF significantly induced the expression of a number of matrix-degrading factors including SAA1, MMP1, MMP3, and MMP13. Simultaneously, a number of cartilage-specific genes including COL2A1, COL9A2, COMP, and LECT were among the most significantly downregulated genes. Conclusions. PEDF represents a marker for transient cartilage during all neonatal and postnatal developmental stages and promotes the termination of cartilage tissue by upregulation of matrix-degrading factors and downregulation of cartilage-specific genes. These data provide the basis for novel strategies to stabilize the phenotype of articular cartilage and prevent its degradation.

Expression of NG2 and platelet-derived growth factor receptor alpha in the developing neonatal rat brain.

Platelet-derived growth factor receptor alpha (PDGFRα) is a marker of oligodendrocyte precursor cells in the central nervous system. NG2 is also considered a marker of oligodendrocyte precursor cells. However, whether there are differences in the distribution and morphology of oligodendrocyte precursor cells labeled by NG2 or PDGFRα in the developing neonatal rat brain remains unclear. In this study, by immunohistochemical staining, NG2 positive (NG2+) cells were ubiquitous in the molecular layer, external pyramidal layer, internal pyramidal layer, and polymorphic layer of the cerebral cortex, and corpus callosum, external capsule, piriform cortex, and medial septal nucleus. NG2+ cells were stellate or fusiform in shape with long processes that were progressively decreased and shortened over the course of brain development. The distribution and morphology of PDGFRα positive (PDGFRα+) cells were coincident with NG2+ cells. The colocalization of NG2 and PDGFRα in the cell bodies and processes of some cells was confirmed by double immunofluorescence labeling. Moreover, cells double-labeled for NG2 and PDGFRα were predominantly in the early postnatal stage of development. The numbers of NG2+/PDGFRα+ cells and PDGFRα+ cells decreased, but the number of NG2+ cells increased from postnatal days 3 to 14 in the developing brain. In addition, amoeboid microglial cells of the corpus callosum, newborn brain macrophages in the normal developing brain, did not express NG2 or PDGFRα, but NG2 expression was detected in amoeboid microglia after hypoxia. The present results suggest that NG2 and PDGFRα are specific markers of oligodendrocyte precursor cells at different stages during early development. Additionally, the NG2 protein is involved in inflammatory and pathological processes of amoeboid microglial cells.

Retinal expression and localization of Mef2c support its important role in photoreceptor gene expression

Photoreceptor-specific gene expression is controlled by a hierarchical network of transcription factors, including the master regulators cone-rod homeobox (Crx) and neural retina leucine zipper (Nrl). Myocyte-enhancer factor 2c (Mef2c) is an ubiquitously expressed transcription factor with important functions in the cardiovascular system. Here, we performed a detailed analysis of Mef2c expression, localization and function in the retina to further elucidate its potential role for photoreceptor gene regulation. We showed that murine retinal Mef2c mRNA expression was high at birth and peaked at late postnatal developmental stages. Using immunohistochemistry and Western blot, Mef2c protein was detected in the outer nuclear layer of adult mouse and human retinas and localized to the nucleus of 661W photoreceptor-like cells. Mef2c knock-down in 661W cells reduced the expression of arrestin 3 (Arr3) and medium-wave-sensitive cone opsin (Opn1mw) but increased transcript levels of mitogen-activated protein kinase 15 (Mapk15) and phosphodiesterase 6h (Pde6h). In conclusion, Mef2c is highly expressed in the retina where it modulates photoreceptor-specific gene expression.

Identifying suitable reference genes for gene expression analysis in developing skeletal muscle in pigs.

The selection of suitable reference genes is crucial to accurately evaluate and normalize the relative expression level of target genes for gene function analysis. However, commonly used reference genes have variable expression levels in developing skeletal muscle. There are few reports that systematically evaluate the expression stability of reference genes across prenatal and postnatal developing skeletal muscle in mammals. Here, we used quantitative PCR to examine the expression levels of 15 candidate reference genes (ACTB, GAPDH, RNF7, RHOA, RPS18, RPL32, PPIA, H3F3, API5, B2M, AP1S1, DRAP1, TBP, WSB, and VAPB) in porcine skeletal muscle at 26 different developmental stages (15 prenatal and 11 postnatal periods). We evaluated gene expression stability using the computer algorithms geNorm, NormFinder, and BestKeeper. Our results indicated that GAPDH and ACTB had the greatest variability among the candidate genes across prenatal and postnatal stages of skeletal muscle development. RPS18, API5, and VAPB had stable expression levels in prenatal stages, whereas API5, RPS18, RPL32, and H3F3 had stable expression levels in postnatal stages. API5 and H3F3 expression levels had the greatest stability in all tested prenatal and postnatal stages, and were the most appropriate reference genes for gene expression normalization in developing skeletal muscle. Our data provide valuable information for gene expression analysis during different stages of skeletal muscle development in mammals. This information can provide a valuable guide for the analysis of human diseases.

Transcriptome Dynamics and Potential Roles of Sox6 in the Postnatal Heart.

The postnatal heart undergoes highly coordinated developmental processes culminating in the complex physiologic properties of the adult heart. The molecular mechanisms of postnatal heart development remain largely unexplored despite their important clinical implications. To gain an integrated view of the dynamic changes in gene expression during postnatal heart development at the organ level, time-series transcriptome analyses of the postnatal hearts of neonatal through adult mice (P1, P7, P14, P30, and P60) were performed using a newly developed bioinformatics pipeline. We identified functional gene clusters by principal component analysis with self-organizing map clustering which revealed organized, discrete gene expression patterns corresponding to biological functions associated with the neonatal, juvenile and adult stages of postnatal heart development. Using weighted gene co-expression network analysis with bootstrap inference for each of these functional gene clusters, highly robust hub genes were identified which likely play key roles in regulating expression of co-expressed, functionally linked genes. Additionally, motivated by the role of the transcription factor Sox6 in the functional maturation of skeletal muscle, the role of Sox6 in the postnatal maturation of cardiac muscle was investigated. Differentially expressed transcriptome analyses between Sox6 knockout (KO) and control hearts uncovered significant upregulation of genes involved in cell proliferation at postnatal day 7 (P7) in the Sox6 KO heart. This result was validated by detecting mitotically active cells in the P7 Sox6 KO heart. The current report provides a framework for the complex molecular processes of postnatal heart development, thus enabling systematic dissection of the developmental regression observed in the stressed and failing adult heart.

GABAρ selective antagonist TPMPA partially inhibits GABA-mediated currents recorded from neurones and astrocytes in mouse striatum

The neostriatum plays a central role in motor coordination where nerve cells operate neuronal inhibition through GABAergic transmission. The neostriatum expresses a wide range of GABA-A subunits, including GABAρ1 and ρ2 which are restricted to a fraction of GABAergic interneurons and astrocytes. Spontaneous postsynaptic currents (sPSCs) evoked by 4-aminopyridine (4-AP) were recorded from neurones of the dorsal neostriatum, and their frequency was reduced > 50% by the selective GABAρ antagonist (1,2,5,6-Tetrahydropyridine-4-yl) methylphosphinic acid (TPMPA). Additionally, we recorded GABA evoked currents from astrocytes in vitro and in situ. Astrocytes in vitro showed modulation by pentobarbital and desensitization upon consecutive applications of GABA. However, modulation by pentobarbital was absent and no significant desensitization was detected from astrocytes in situ. Moreover, TPMPA-sensitive GABA-currents that were insensitive to bicuculline were also recorded from astrocytes in situ, consistent with our previous study where GABAρ expression was demonstrated. Finally, we assessed the mRNA expression of GABAρ3, through different stages of postnatal development; double immunofluorescence disclosed GABAρ3 expression in calretinin-positive interneurons as well as in astrocytes (>70%). These results add new information about the participation of GABAρ subunits in neostriatal interneurons and astrocytes.

Calcium-induced apoptosis of developing cerebellar granule neurons depends causally on NGFI-B

Immediate early gene nerve growth factor-induced clone B (NGFI-B), a nuclear receptor important for differentiation and apoptosis, is expressed in mice and rat cerebellum from an early stage of postnatal development. Following apoptotic stimuli NGFI-B translocates to mitochondria to initiate cell death processes. Controlled cell death is critical for correct cerebellar development. Immunohistochemical analysis of NGFI-B in sections of mice cerebella showed NGFI-B to be expressed in granule neurons in vivo at a time (P8-11) when apoptosis is known to occur. The importance of NGFI-B for apoptosis of cultured rat cerebellar granule neurons was investigated by inducing apoptosis with calcium ionophore A23187 (CaI, 0.1μM). Imaging studies of gfp-tagged NGFI-B confirmed that mitochondrial translocation of NGFI-B occurred following treatment with CaI and was reduced by addition of 9-cis-retinoic acid (1μM), a retinoid X receptor (RXR) agonist that prevents dimerization of RXR and NGFI-B that is known to occur before translocation. Consequently, 9-cis-retinoic acid partly reduced cell death. To address the causality of NGFI-B in apoptosis further, knock-down by siRNA was performed and it removed 85% of the NGFI-B protein. This resulted in a complete inhibition of apoptosis after CaI exposure. Together these findings suggest that NGFI-B plays a role in controlling correct cerebellar development.