The Canadian healthy infant longitudinal development birth cohort study: biological samples and biobanking

BACKGROUND

It is hypothesised that complex interactions between genetic and environmental factors give rise to allergy and asthma in childhood. The Canadian Healthy Infant Longitudinal Development (CHILD) study was designed to explore these factors.

METHODS

CHILD is a longitudinal, general population birth cohort study following infants from mid-pregnancy to age 5 years. Over this time period, biological samples, questionnaires, clinical measures and environmental data are collected.

RESULTS

A total of 3624 families have been recruited, and many thousands of samples and questionnaires have been collected, annotated, and archived. This report outlines the rationale and methodology for collecting and storing diverse biological samples from parents and children in this study, and the mechanisms for their release for analyses.

CONCLUSIONS

The CHILD sample and data repository is a tremendous current and future resource and will provide a wealth of information not only informing studies of asthma and allergy, but also potentially in many other aspects of health relevant for Canadian infants and children.

Identification and characterization of a novel sucrose-non-fermenting protein kinase/AMP-activated protein kinase-related protein kinase, SNARK

Subtraction hybridization after the exposure of keratinocytes to ultraviolet radiation identified a differentially expressed cDNA that encodes a protein of 630 amino acid residues possessing significant similarity to the catalytic domain of the sucrose-non-fermenting protein kinase (SNF1)/AMP-activated protein kinase (AMPK) family of serine/threonine protein kinases. Northern blotting and reverse-transcriptase-mediated PCR demonstrated that mRNA transcripts for the SNF1/AMPK-related kinase (SNARK) were widely expressed in rodent tissues. The SNARK gene was localized to human chromosome 1q32 by fluorescent in situ hybridization. SNARK was translated in vitro to yield a single protein band of approx. 76 kDa; Western analysis of transfected baby hamster kidney (BHK) cells detected two SNARK-immunoreactive bands of approx. 76-80 kDa. SNARK was capable of autophosphorylation in vitro; immunoprecipitated SNARK exhibited phosphotransferase activity with the synthetic peptide substrate HMRSAMSGLHLVKRR (SAMS) as a kinase substrate. SNARK activity was significantly increased by AMP and 5-amino-4-imidazolecarboxamide riboside (AICAriboside) in rat keratinocyte cells, implying that SNARK might be activated by an AMPK kinase-dependent pathway. Furthermore, glucose deprivation increased SNARK activity 3-fold in BHK fibroblasts. These findings identify SNARK as a glucose- and AICAriboside-regulated member of the AMPK-related gene family that represents a new candidate mediator of the cellular response to metabolic stress.

Characterization of fertilization-modulated myelin basic protein kinases from sea star: regulation of Mapk

The myelin basic protein (MBP)-phosphorylating enzymes present during maturation and early embryogenesis of the sea star (Pisaster ochraceus) were investigated. The major maturation-activated MBP kinase (p45 Mapk) was molecularly cloned based on tryptic sequence information obtained with the purified enzyme and shown to be highly related to human Erk1 with 76% amino acid identity. Kinase assays and immunoblotting studies revealed that Mapk remained highly active until 12 h post-fertilization (PF), after which it declined. By 4 days PF, Mapk protein was no longer detectable. At 3 h PF, about half of the detectable MBP phosphotransferase activity could be attributed to a 75 kDa protein kinase that was distinct from Mapk. Like Mapk, this protein phosphorylated MBP mostly on threonine residues, but it failed to phosphorylate a peptide (APRTPGGRR) based upon the Thr-97 MAP kinase phosphorylation site in MBP. Rather, it phosphorylated a peptide (AAQKRPSQRTKYLA) patterned after the N-terminus of MBP. Our studies also showed a dramatic increase in MBP phosphotransferase activity occurred by 4 days PF that arose from a third kinase that phosphorylated MBP solely on serine residues. This kinase exhibited the following substrate substrate preference: AAQKRPSQRTKYLA, peptide substrate for S6 kinases (AKRRRLSSLRASTSKSESSQK) > MBP > histone H1 > prota-mine > casein > APRTPGGRR. This kinase was not appreciably affected by addition of phosphatidylserine/diacylglycerol, or the staurosporine analogue Roche Compound 3, but it was partly inhibited by a protein kinase C pseudosubstrate peptide. Gel filtration analysis revealed an apparent molecular mass of 41 kDa for the enzyme. Therefore, at least two novel MBP-phosphorylating enzymes distinct from Mapk are preferentially activated following fertilization and early embryogenesis of the sea star.

UVB and gamma-radiation induce the expression of mRNAs encoding the ribosomal subunit L13A in rat keratinocytes

Ultraviolet B radiation produces an array of cellular perturbations in the skin. We isolated a keratinocyte cDNA encoding the rat 60S ribosomal subunit protein L13a following differential cDNA library screening with UVB-enriched probes. In contrast to the reported structure of liver L13a, the keratinocyte L13a cDNA contains a longer 3'-untranslated region. Northern blot analysis detected two L13a mRNA transcripts, approximately 800 bp and approximately 1.2 kb, in keratinocytes and a variety of rat tissues. Both L13a mRNA transcripts were induced by UVB irradiation, forskolin and gamma-irradiation. In contrast, no induction of L13a mRNA transcript levels was observed following exposure of keratinocytes to 12-O-tetradecanoylphorbol-13-acetate, serum and the DNA damage-inducing agents methyl methanesulfonate or 4-nitroquinoline-N-oxide. These observations suggest that increased expression of ribosomal subunit genes may be a molecular component of the keratinocyte response to UVB in particular and not part of a nonspecific response to DNA damage.

Myometrial transcriptional regulation of the gap junction gene, connexin-43

The mechanisms that enable the myometrium to switch from a state of relative quiescence during pregnancy to a muscle that is spontaneously active, very responsive to endogenous uterotonins and exhibits a high degree of cell-cell coordination are poorly understood. It is hypothesized that this switch or 'activation' of the myometrium results from the coordinated expression of a cassette of 'contraction-associated proteins'. The molecular mechanisms that regulate the expression of one of these, namely the myometrial gap junction protein connexin-43 (Cx-43), have been analysed. Myometrial Cx-43 expression is significantly increased during labour, associated with an increase in plasma oestrogen:progesterone, and positively regulated by oestrogen in non-pregnant rats. The genomic structure of the murine Cx-43 gene and the sequence of its 5' flanking sequence are reported here. This region functions as a promoter and contains several putative cis-acting elements which may be important in the regulation of Cx-43 transcription. Among these elements are several half-palindromic sequences that may function as oestrogen response elements and several AP-1 sites that may bind the transcription factors Fos and Jun. Oestrogen treatment of cells transiently transfected with a plasmid containing the Cx-43 promoter linked to the chloramphenicol acetyl transferase (CAT) gene, increased CAT activity indicating that the murine Cx-43 gene is oestrogen responsive. In addition, treatment of rats with oestrogen significantly increased mRNA encoding c-fos and c-jun in the myometrium and this occurred before any increase in Cx-43 mRNA. These data suggest that oestrogen may increase transcription of the Cx-43 gene through direct mechanisms (via the putative oestrogen response elements) or indirect mechanisms (by increased expression of c-fos and c-jun acting via the putative AP-1 sites). Since oestrogen may be an important modulator of myometrial activation, these mechanisms may be critical to the processes leading to increased synthesis of gap junctions at term and, hence, to the onset of labour.

Uterine oxytocin gene expression. I. Induction during pseudopregnancy and the estrous cycle

We have recently demonstrated that the gene encoding the hypothalamic peptide oxytocin (OT) is highly expressed in the rat endometrial epithelium during the last 4 days of pregnancy. Here, we show that uterine OT gene expression is also induced during the proestrous phase of the estrous cycle and after induction of pseudopregnancy. In mature female rats, OT mRNA levels increased more than 10-fold between diestrus and proestrus and remained elevated at estrus. The levels attained at estrus corresponded to about 1/20th of the levels present at term. In immature rats rendered pseudopregnant by treatment with pregnant mare serum and hCG, uterine OT mRNA levels rose steadily and reached a maximum on day 14 of pseudopregnancy, corresponding to about 1/8th of the levels observed on day 21 of normal pregnancy. Oil-induced decidualization of the left uterine horn prolonged pseudopregnancy and maintained OT mRNA levels in both uterine horns until day 19 of pseudopregnancy. These changes were tissue specific, as hypothalamic OT mRNA levels remained essentially unaffected. The present findings demonstrate that either spontaneous or induced changes in endogenous steroid levels are capable of eliciting important changes in uterine, but not hypothalamic, OT gene expression.

Uterine oxytocin gene expression. II. Induction by exogenous steroid administration

As we have recently shown, the gene encoding the hypothalamic nonapeptide oxytocin (OT) is expressed in the rat endometrial epithelium during late pregnancy and the estrous phase of the estrous cycle. To investigate the role of ovarian steroids in the regulation of uterine OT gene expression, Silastic capsules containing estradiol or progesterone were implanted into immature ovariectomized rats. Exposure to estradiol alone for 2 days caused a significant rise in OT mRNA. Administration of progesterone alone was without effect. However, a strong synergism was observed when the two hormones were applied together; progesterone potentiated the effect of estradiol by a factor of 7. In animals treated with steroids for 4 days, the removal of either the estradiol or progesterone capsule after day 2 led to a decrease in the total amount of OT mRNA accumulation, implying that the continued action of both steroids was required to achieve maximal OT mRNA levels. Immunocytochemical analysis demonstrated that the main site of steroid-induced uterine OT gene expression is the endometrial epithelium, the same site where endogenously induced OT gene expression occurs at the end of pregnancy. The OT mRNA levels achieved after 4 days of treatment with both steroids were comparable to those achieved at estrus or during pseudopregnancy, but corresponded to less than 20% of the levels present in the uterus on day 21 of pregnancy. These data suggest that in the uterus, the synergistic action of ovarian steroids represents an important, but probably not exclusive, regulator of OT gene expression.

Rat amnion: a novel site of oxytocin production

Fetal membranes, in addition to serving as passive barriers, possess secretory capacities and have a role in amniotic fluid production. In the present study, we demonstrate that rat amniotic/chorionic membranes have the capacity to synthesize oxytocin (OT). Analysis of RNA extracted from rat amnion/chorion membranes by RNA blotting and polymerase chain reaction (PCR) revealed the presence of a single species of OT mRNA. The transcript was smaller than the hypothalamic OT transcript and equaled the size of uterine and placental OT mRNA. The abundance of amniotic OT mRNA decreased by 37% from Day 14 to Day 21 of pregnancy. Over the same time, amniotic/chorionic OT immunoreactivity, as assessed by RIA, increased from 0.17 +/- 0.03 to 1.36 +/- 0.18 ng/g tissue weight. HPLC analysis of amniotic/chorionic membrane extracts revealed two peaks of immunoreactive OT (ir-OT). The first peak (36% of total ir-OT) co-eluted with synthetic OT, while the second peak (64%) corresponded to a noncovalent complex, most likely between OT and neurophysin-I. Using the selective OT receptor ligand, 125I-d(CH2)5 [Tyr(Me)2,Thr4,Tyr-NH2(9)]OVT, we detected high numbers of OT binding sites in rat uterine tissues, but no OT binding sites in amniotic/chorionic or placental membranes. We conclude that the rat amniotic/chorionic membranes represent an extra-hypothalamic site of OT gene expression in the rat during pregnancy and thus represent a possible source of OT present in amniotic fluid.

Oxytocin gene expression in rat uterus

The neurohypophyseal hormone oxytocin (OT) is the most potent uterotonic agent known and is used to induce labor. Yet, endogenous circulating OT appears not to participate in the induction of labor. As shown here, the finding of OT messenger RNA and peptide in the uterus suggests a solution for this paradox. During gestation, rat uterus OT messenger RNA increased more than 150-fold and, at term, exceeded hypothalamic OT messenger RNA by 70-fold. Thus, during parturition, OT may act primarily as a local mediator and not as a circulating hormone.

Expression of the oxytocin gene in rat placenta

The placenta is an endocrinologically active organ and expresses an important number of polypeptide hormone genes. Although oxytocin (OT)-like immunoreactivity has been detected in placental extracts by RIA, the precise nature and origin of placental OT has remained unclear. In the present study, we examined OT gene expression in rat placental tissue at various stages of gestation using northern blot analysis, polymerase chain reaction, in situ hybridization, HPLC, and immunocytochemistry. Northern blot analysis of RNA extracted from rat placenta revealed a single type of OT gene transcript (0.66 kilobases) which differed in size from hypothalamic OT transcripts (0.75 kilobases). Deadenylation of placental and hypothalamic messenger RNA (mRNA) showed that this size difference was due to differences in poly(A) tail lengths. Polymerase chain reaction amplification of placental and hypothalamic complementary DNAs using four different exon-specific primers provided no evidence for the existence of any additional structural differences between hypothalamic and placental OT-gene transcripts. Quantitative evaluation of northern blots showed that OT mRNA abundance per microgram of total RNA was stage specific and declined by a factor of 6 from day 14 to day 21 of gestation. In contrast to the marked variation of mRNA abundance, the OT peptide content, as measured by RIA, underwent no significant change during the time period studied and varied between 0.37-0.51 ng/g wet tissue wt. Characterization of placental OT immunoreactivity by HPLC and gel filtration identified two peaks of immunoreactivity: one peak (70% of immunoreactivity) corresponded to synthetic OT; whereas the other peak (Mr 11,000, 30% of immunoreactivity) represented a noncovalent association between OT and another molecule, consistent with the formation of a neurophysin/OT complex. By in situ hybridization and immunocytochemistry, we localized OT mRNA and OT immunoreactivity to cells of the trophoblastic epithelium covering the septa of the labyrinth as well as to cytotrophoblastic elements and giant cells of the maternally derived basal zone of the placenta. Placental OT may act locally, may interact with uterine OT receptors, or may play a role in fetal development.

Novel vasopressin gene-related transcripts in rat testis

Although the arginine vasopressin (AVP) gene is predominantly expressed in specific hypothalamic neurons, immunoreactive AVP (irAVP) has also been identified in peripheral tissues, including testis. To determine whether hypothalamic and testicular ir-AVPs derive from the same or different transcripts, we examined testicular AVP gene-related transcripts by Northern blot analysis, polymerase chain reaction (PCR), and RNase mapping. We show that the testis contains three distinct AVP gene-related transcripts of 0.67, 0.83, and 2.0 kilobases (kb) which differ in size from the 0.81-kb hypothalamic AVP mRNA. As demonstrated by deadenylation, this size heterogeneity is not due to differences in the length of the poly(A) tails. By the use of exon-specific probes we determined that the 0.67- and the 0.83-kb transcripts contain exons B and C, but not A. In contrast, the 2-kb transcript is the only testicular transcript that contains an exon A-related sequence. By application of the PCR technique, we confirm the existence of testicular transcripts in which exons B and C are spliced together, but exon A is excluded. Our findings indicate that the 0.67- and 0.83-kb mRNA results from a differential splicing event that excludes exon A and that the 2-kb mRNA probably originates from the expression of an AVP-related gene. Since the nonapeptide AVP is encoded by exon A, testicular irAVP cannot arise from the translation of any of the exon B- and C-containing transcripts, and any mRNA that has so far been identified by AVP exon C probes is unrelated to the biosynthesis of AVP-immunoreactive products.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxytocin mRNA: increase of polyadenylate tail size during pregnancy and lactation

Earlier studies indicate that rat hypothalamic oxytocin (OT) mRNA accumulation rises gradually during pregnancy and remains elevated throughout the lactation period. Here we show that, in addition, hypothalamic OT mRNA undergoes a structural change during this period. On gel electrophoresis, the size of rat OT mRNA increased from 750 bases (control) to a maximum of 820 bases (7th day of lactation). Removal of the poly(A) tail by the RNase H methods revealed that this size increase can be fully accounted for by a prolongation of the polyadenylate tail. There is considerable evidence for a role of the poly(A) tail segment in augmenting mRNA stability and, possibly, translational efficiency. It is thus conceivable that the demonstrated regulation of OT mRNA poly(A) tail length represents an additional level of OT gene control during pregnancy and lactation.

Ontogeny of hypothalamic vasopressin, oxytocin and somatostatin gene expression

The expression of 3 neuropeptide genes, vasopressin (AVP), oxytocin (OT) and somatostatin (SOM), was studied in the developing rat hypothalamus using Northern blot analysis combined with densitometric scanning. A unique profile of developmental expression was established for each of the 3 genes. SOM mRNA is detectable at embryonic day 14 and reaches 40% of the adult levels by embryonic day 18. By contrast, accumulation of AVP and OT mRNA is mainly a postnatal event. AVP mRNA, although detectable in the late embryo, rises gradually after birth and attains 40% of adult levels after the second postnatal week. Maturation of OT gene expression occurs even later and parallels AVP gene expression with a lag time of one week. Observed increases in mRNA levels are due to an upregulation of gene expression since they occur essentially following cessation of neuronal cell proliferation. The rise in AVP and OT mRNA accumulation coincides with the establishment of synaptic input to AVP and OT neurons. Expression of the SOM gene, by contrast, occurs prior to neuronal cell differentiation and points to a possible function of SOM in the embryonic brain.

Regulation of poly(A) tail size of vasopressin mRNA

Dehydration represents a strong stimulus for the secretory activity of hypothalamic vasopressinergic neurons and induces a sustained rise in hypothalamic [Arg8]vasopressin (AVP) mRNA. We now report that, in addition to the change in mRNA accumulation, this stimulus leads to an increase in the size of the mature AVP gene transcripts. Using Northern blot analysis in conjunction with internal RNA size markers, we demonstrate here that a 6-day period of salt imbibition induced a gradual size increase of AVP mRNA from 810 to a maximum of 930 bases. This change was fully reversed by day 30 following termination of the salt treatment. Any alteration of the mRNA capping or polyadenylation sites was ruled out by S1 mapping. However, poly(A) tail removal reduced AVP mRNA of all treatment groups to exactly the same size (600 bases). It is concluded that the dehydration-induced size change is due to a greater than 50% increase of the mean steady state length of the poly(A) tail. It remains to be determined to what extent the observed increase in poly(A) tail length may have an effect on AVP mRNA stability or translational efficiency.

Oxytocin and vasopressin gene expression during gestation and lactation

Levels of rat hypothalamic oxytocin (OT) and vasopressin (AVP) mRNA were determined during gestation and lactation using a densitometric hybridization assay. Pregnancy induced a gradual rise in OT mRNA, reaching, by day 18, a level exceeding control by a factor of 2.5. Throughout the lactation period OT mRNA remained elevated at levels corresponding to 3 times that of control. Surprisingly, the dynamics of AVP mRNA accumulation paralleled closely the profile observed for OT mRNA throughout the time period studied. We conclude that in late pregnancy and lactation the expression of both, the OT and the AVP gene is stimulated in parallel by mechanisms operating at a pretranslational level, involving increased gene transcription or mRNA stabilization, or both. Further characterization of the two mRNA species revealed that both mRNAs are endowed with very long poly(A) tails of greater than 200 nucleotides, under conditions of both, normal and stimulated states of gene expression. The role, if any, of the prolonged poly(A) tails in mRNA stability remains to be determined.