Optimal His-Tag Design for Efficient [99mTc(CO)3]+ and [188Re(CO)3]+ Labeling of Proteins for Molecular Imaging and Radionuclide Therapy by Analysis of Peptide Arrays.

Hexahistidine tags (His-tags), incorporated into recombinant proteins to facilitate purification using metal-affinity chromatography, are useful binding sites for radiolabeling with [99mTc(CO)3]+ and [188Re(CO)3]+ for molecular imaging and radionuclide therapy. Labeling efficiencies vary unpredictably, and the method is therefore not universally useful. To overcome this, we have made quantitative comparisons of radiolabeling of a bespoke Celluspots array library of 382 His-tag-containing peptide sequences with [99mTc(CO)3]+ and [188Re(CO)3]+ to identify key features that enhance labeling. A selected sequence with 10-fold enhanced labeling efficiency compared to the most effective literature-reported sequences was incorporated into an exemplar protein and compared biologically with non-optimized analogues, in vitro and in vivo. Optimal labeling with either [99mTc(CO)3]+ or [188Re(CO)3]+ required six consecutive His residues in the protein sequence, surrounded by several positively charged residues (Arg or Lys), and the presence of phosphate in the buffer. Cys or Met residues in the sequence were beneficial, to a lesser extent. Negatively charged residues were deleterious to labeling. His-tags with adjacent positively charged residues could be labeled as much as 40 times more efficiently than those with adjacent negatively charged residues. 31P NMR of [Re(CO)3(H2O)3]+ and electrophoresis of solutions of [99mTc(CO)3(H2O)3]+ suggest that phosphate bridges form between cationic residues and the cationic metal synthon during labeling. The trial optimized protein, a scFv targeted to the PSMA antigen expressed in prostate cancer, was readily labeled in >95% radiochemical yield, without the need for subsequent purification. Labeling occurred more quickly and to higher specific activity than comparable non-optimized proteins, while retaining specific binding to PSMA and prostate cancer in vivo. Thus, optimized His-tags greatly simplify radiolabeling of recombinant proteins making them potentially more widely and economically available for imaging and treating patients.

Variants on chromosome 4q21 near PKD2 and SIBLINGs are associated with dental caries.

A recent genome-wide association study (GWAS) for dental caries nominated the chromosomal region 4q21 near ABCG2, PKD2 and the SIBLING (small integrin-binding ligand N-linked glycoprotein) gene family. In this investigation, we followed up and fine-mapped this region using a tag-SNP (single-nucleotide polymorphism) approach in 13 age- and race-stratified samples from 6 independent studies (N=4089). Participants were assessed for dental caries via intraoral examination and 49 tag-SNPs were genotyped capturing much of the variation in the 4q21 locus. Linear models were used to test for genetic association, while adjusting for sex, age and components of ancestry. SNPs in and near PKD2 showed significant evidence of association in individual samples of black adults (rs17013735, P-value=0.0009) and white adults (rs11938025; P-value=0.0005; rs2725270, P-value=0.003). Meta-analyses across black adult samples recapitulated the association with rs17013735 (P-value=0.003), which occurs at low frequency in non-African populations, possibly explaining the race specificity of the effect. In addition to race-specific associations, we also observed evidence of gene-by-fluoride exposure interaction effects in white adults for SNP rs2725233 upstream of PKD2 (P=0.002). Our results show evidence of regional replication, though no single variant clearly accounted for the original GWAS signal. Therefore, while we interpret our results as strengthening the hypothesis that chromosome 4q21 may impact dental caries, additional work is needed.

Exploring Subclinical Phenotypic Features in Twin Pairs Discordant for Cleft Lip and Palate.

OBJECTIVE: Monozygotic twins of an individual with an orofacial cleft have a significantly elevated risk for orofacial cleft compared with the general population, but still the concordance rate for orofacial cleft in monozygotic twins is about 40% to 50%. The goal of this study was to determine whether unaffected cotwins have an increased frequency of orbicularis oris muscle defects, a subclinical form of orofacial cleft. The presence of such defects may reduce the overall rate of discordance. METHOD: A total of 63 discordant monozygotic and dizygotic twin pairs, 262 unaffected nontwin siblings, and 543 controls with no history of orofacial clefts were assessed for orbicularis oris defects by high-resolution ultrasound. Frequencies were compared by the Fisher exact test. RESULTS: Unaffected cotwins from discordant monozygotic pairs had a higher frequency of defects (12.5%) than the other test groups (6.38% to 6.99%), but the difference was not statistically significant (P = .74). CONCLUSIONS: In this study, orbicularis oris defects were not statistically significantly more common among the unaffected twins from orofacial cleft discordant twin pairs. The trends in the results warrant future studies with larger sample sizes and additional subclinical phenotypes.

Ear Infection in Isolated Cleft Lip: Etiological Implications.

BACKGROUND AND HYPOTHESIS: Chronic ear infections are a common occurrence in children with orofacial clefts involving the secondary palate. Less is known about the middle ear status of individuals with isolated clefts of the lip, although several studies have reported elevated rates of ear infection in this group. The purpose of this retrospective study was to test the hypothesis that chronic ear infections occur more frequently in isolated cleft lip cases (n = 94) compared with controls (n = 183). METHODS: A questionnaire was used to obtain information on history of chronic ear infection. The association between ear infection status (present/absent) and cleft lip status (cleft lip case/control) was tested using both chi-square and logistic regression. RESULTS AND CONCLUSIONS: The reported occurrence of chronic ear infection was significantly greater in cleft lip cases (31%) compared with unaffected controls (11%). After adjusting for age and sex, having a cleft lip increased the odds of being positive for ear infection by a factor greater than 3 (odds ratio = 3.698; 95% confidence interval = 1.91 to 7.14). Within cleft lip cases, there was no difference in the occurrence of ear infection by defect laterality or by the type of clefting present in the family history. Although velopharyngeal insufficiency was present in 18.4% of our cleft lip sample, there was no statistical association between ear infection and abnormal speech patterns. These results may have potential implications both for the clinical management of isolated cleft lip cases and for understanding the etiology of orofacial clefting.

In-Cell Activation of Organo-Osmium(II) Anticancer Complexes.

The family of iodido OsII arene phenylazopyridine complexes [Os(η6 -p-cym)(5-R1 -pyridylazo-4-R2 -phenyl))I]+ (where p-cym=para-cymene) exhibit potent sub-micromolar antiproliferative activity towards human cancer cells and are active in vivo. Their chemical behavior is distinct from that of cisplatin: they do not readily hydrolyze, nor bind to DNA bases. We report here a mechanism by which they are activated in cancer cells, involving release of the I- ligand in the presence of glutathione (GSH). The X-ray crystal structures of two active complexes are reported, 1-I (R1 =OEt, R2 =H) and 2-I (R1 =H, R2 =NMe2 ). They were labelled with the radionuclide 131 I (ß- /γ emitter, t1/2 8.02 d), and their activity in MCF-7 human breast cancer cells was studied. 1-[131 I] and 2-[131 I] exhibit good stability in both phosphate-buffered saline and blood serum. In contrast, once taken up by MCF-7 cells, the iodide ligand is rapidly pumped out. Intriguingly, GSH catalyzes their hydrolysis. The resulting hydroxido complexes can form thiolato and sulfenato adducts with GSH, and react with H2 O2 generating hydroxyl radicals. These findings shed new light on the mechanism of action of these organo-osmium complexes.

Genetic Modifiers of Patent Ductus Arteriosus in Term Infants.

OBJECTIVE: To identify single-nucleotide polymorphisms (SNPs) in specific candidate genes associated with patent ductus arteriosus in term infants. STUDY DESIGN: We conducted an initial family-based, candidate gene study to analyze genotype data from DNA samples obtained from 171 term infants and their parents enrolled in the National Birth Defects Prevention Study (NBDPS). We performed transmission disequilibrium testing (TDT) using a panel of 55 SNPs in 17 genes. Replication of SNPs with P < .1 in the NBDPS trios was performed with a case-control strategy in an independent population. RESULTS: TDT analysis of the NBDPS trios resulted in 6 SNPs reaching the predetermined cutoff (P < .1) to be included in the replication study. These 6 SNPs were genotyped in the independent case-control population. A SNP in TGFBR2 was found to be associated with term patent ductus arteriosus in both populations after we corrected for multiple comparisons. (rs934328, TDT P = 2 × 10(-4), case-control P = 6.6 × 10(-5)). CONCLUSIONS: These findings confirm the importance of the transforming growth factor-beta pathway in the closure of the term ductus arteriosus and may suggest new therapeutic targets.

Effects of enamel matrix genes on dental caries are moderated by fluoride exposures.

Dental caries (tooth decay) is the most common chronic disease, worldwide, affecting most children and adults. Though dental caries is highly heritable, few caries-related genes have been discovered. We investigated whether 18 genetic variants in the group of non-amelogenin enamel matrix genes (AMBN, ENAM, TUFT1, and TFIP11) were associated with dental caries experience in 13 age- and race-stratified samples from six parent studies (N = 3,600). Linear regression was used to model genetic associations and test gene-by-fluoride interaction effects for two sources of fluoride: daily tooth brushing and home water fluoride concentration. Meta-analysis was used to combine results across five child and eight adult samples. We observed the statistically significant association of rs2337359 upstream of TUFT1 with dental caries experience via meta-analysis across adult samples (p < 0.002) and the suggestive association for multiple variants in TFIP11 across child samples (p < 0.05). Moreover, we discovered two genetic variants (rs2337359 upstream of TUFT1 and missense rs7439186 in AMBN) involved in gene-by-fluoride interactions. For each interaction, participants with the risk allele/genotype exhibited greater dental caries experience only if they were not exposed to the source of fluoride. Altogether, these results confirm that variation in enamel matrix genes contributes to individual differences in dental caries liability, and demonstrate that the effects of these genes may be moderated by protective fluoride exposures. In short, genes may exert greater influence on dental caries in unprotected environments, or equivalently, the protective effects of fluoride may obviate the effects of genetic risk alleles.

Replication of 13q31.1 association in nonsyndromic cleft lip with cleft palate in Europeans.

Genome wide association (GWA) studies have successfully identified at least a dozen loci associated with orofacial clefts. However, these signals may be unique to specific populations and require replication to validate and extend findings as a prelude to etiologic SNP discovery. We attempted to replicate the findings of a recent meta-analysis of orofacial cleft GWA studies using four different ancestral populations. We studied 946 pedigrees (3,436 persons) of European (US white and Danish) and Asian (Japanese and Mongolian) origin. We genotyped six SNPs that represented the most significant P-value associations identified in published studies: rs742071 (1p36), rs7590268 (2p21), rs7632427 (3p11.1), rs12543318 (8q21.3), rs8001641 (13q31.1), and rs7179658 (15q22.2). We directly sequenced three non-coding conserved regions 200 kb downstream of SPRY2 in 713 cases, 438 controls, and 485 trios from the US, Mongolia, and the Philippines. We found rs8001641 to be significantly associated with nonsyndromic cleft lip with cleft palate (NSCLP) in Europeans (P-value = 4 × 10(-5), ORtransmission = 1.86 with 95% confidence interval: 1.38-2.52). We also found several novel sequence variants in the conserved regions in Asian and European samples, which may help to localize common variants contributing directly to the risk for NSCLP. This study confirms the prior association between rs8001641 and NSCLP in European populations.

Cycles of adaptive strategies over the life course.

An increasing number of Australia's ageing population are aging with long-term physical impairments. This study explored the life experiences of this group using a qualitative approach. In-depth interviews were conducted with 10 disabled Victorians, aged between 51 and 84 years, and an inductive thematic analysis undertaken. A relationship was found between the adaptive strategies that participants developed as they moved through life phases and the impairment stages. The implications of the emergence of a cyclical process of adaptation across the life course. and particularly in respect of aging, delivery of aged-care services and social workers in this sector are discussed.

Evaluation of Antibiotic Use for Dental-Related Infections in Dental Clinics Associated With an Academic Safety Net Institution.

This retrospective study found lower antibiotic prescribing rates by outpatient dentists than previous literature, but with deviations from guideline recommendations in antibiotic indications and durations of treatment for oral pain and swelling. These findings will guide future stewardship interventions to promote guideline-directed therapy plans.

Efficient bone marrow irradiation and low uptake by non-haematological organs with an yttrium-90-anti-CD66 antibody prior to haematopoietic stem cell transplantation.

We report the results of a Phase I radiation dose escalation study using an yttrium-90 (90Y) labelled anti-CD66 monoclonal antibody given with standard conditioning regimen for patients receiving haematopoietic stem cell transplants for myeloid leukaemia or myeloma. The 90Y-labelled anti-CD66 was infused prior to standard conditioning. In total, 30 patients entered the trial and 29 received 90Y-labelled mAb, at infused radiation activity levels of 5, 10, 25, or 37.5 megaBequerel (MBq)/kg lean body weight. A prerequisite for receiving the 90Y-labelled mAb was favourable dosimetry determined by single-photon emission computerised tomography (SPECT) dosimetry following administration of indium-111 (111In) anti-CD66. Estimated absorbed radiation doses delivered to the red marrow demonstrated a linear relationship with the infused activity of 90Y-labelled mAb. At the highest activity level of 37.5 MBq/kg, mean estimated radiation doses for red marrow, liver, spleen, kidneys and lungs were 24.6 ± 5.6 Gy, 5.8 ± 2.7 Gy, 19.1 ± 8.0 Gy, 2.1 ± 1.1 and 2.2 ± 0.9, respectively. All patients engrafted, treatment-related mortality 1-year post-transplant was zero. Toxicities were no greater than those anticipated for similar conditioning regimens without targeted radiation. The ability to substantially intensify conditioning prior to haematopoietic stem cell transplantation without increasing toxicity warrants further testing to determine efficacy. clinicaltrials.gov identifier: NCT01521611.

Radiotracers for in situ infection imaging: Experimental considerations for in vitro microbial uptake of gallium-68-labeled siderophores.

In vitro screening of gallium-68(68Ga)-siderophores in pathogens relevant to infections is valuable for determining species specificity, their effect on cell viability, and potential clinical applications. As the recognition and internalization of siderophores relies on the presence of receptor- and/or siderophore-binding proteins, the level of uptake can vary between species. Here, we report in vitro uptake validation in Escherichia coli with its native siderophore, enterobactin (ENT) ([68Ga]Ga-ENT), considering different experimental factors. Compared with other reporting methods of uptake, '% Added dose/109 CFU/mL (% AD/109 CFU/mL),' considering the total viable count, showed a better comparison among microbial species. Later, in vitro screening with [68Ga]Ga-desferrioxamine B (DFO-B) showed high uptake by Staphylococcus aureus and S. epidermidis; moderate uptake by Pseudomonas aeruginosa; poor uptake by E. coli, Candida albicans, and Aspergillus fumigatus; and no uptake by Enterococcus faecalis and C. glabrata. Except for S. epidermidis, [68Ga]Ga-DFO-B did not reduce the cell viability.

[68Ga]Ga-Schizokinen, a Potential Radiotracer for Selective Bacterial Infection Imaging.

Gallium-68-labeled siderophores as radiotracers have gained interest for the development of in situ infection-specific imaging diagnostics. Here, we report radiolabeling, in vitro screening, and in vivo pharmacokinetics (PK) of gallium-68-labeled schizokinen ([68Ga]Ga-SKN) as a new potential radiotracer for imaging bacterial infections. We radiolabeled SKN with ≥95% radiochemical purity. Our in vitro studies demonstrated its hydrophilic characteristics, neutral pH stability, and short-term stability in human serum and toward transchelation. In vitro uptake of [68Ga]Ga-SKN by Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and S. epidermidis, but no uptake by Candida glabrata, C. albicans, or Aspergillus fumigatus, demonstrated its specificity to bacterial species. Whole-body [68Ga]Ga-SKN positron emission tomography (PET) combined with computerized tomography (CT) in healthy mice showed rapid renal excretion with no or minimal organ uptake. The subsequent ex vivo biodistribution resembled this fast PK with rapid renal excretion with minimal blood retention and no major organ uptake and showed some dissociation of the tracer in the urine after 60 min postinjection. These findings warrant further evaluation of [68Ga]Ga-SKN as a bacteria-specific radiotracer for infection imaging.

Role of TRAV locus in low caries experience.

Caries is the most common chronic, multifactorial disease in the world today; and little is still known about the genetic factors influencing susceptibility. Our previous genome-wide linkage scan has identified five loci related to caries susceptibility: 5q13.3, 13q31.1, 14q11.2, 14q 24.3, and Xq27. In the present study, we fine mapped the 14q11.2 locus to identify genetic contributors to caries susceptibility. Four hundred seventy-seven subjects from 72 pedigrees with similar cultural and behavioral habits and limited access to dental care living in the Philippines were studied. An additional 387 DNA samples from unrelated individuals were used to determine allele frequencies. For replication purposes, a total of 1,446 independent subjects from four different populations were analyzed based on their caries experience (low versus high). Forty-eight markers in 14q11.2 were genotyped using TaqMan chemistry. Transmission disequilibrium test was used to detect over transmission of alleles in the Filipino families, and Chi-square, Fisher's exact and logistic regression were used to test for association between low caries experience and variant alleles in the replication data sets. We finally assessed the mRNA expression of TRAV4 in the saliva of 143 study subjects. In the Filipino families, statistically significant associations were found between low caries experience and markers in TRAV4. We were able to replicate these results in the populations studied that were characteristically from underserved areas. Direct sequencing of 22 subjects carrying the associated alleles detects one missense mutation (Y30R) that is predicted to be probably damaging. Finally, we observed higher expression in children and teenagers with low caries experience, correlating with specific alleles in TRAV4. Our results suggest that TRAV4 may have a role in protecting against caries.

Sequence variants in oxytocin pathway genes and preterm birth: a candidate gene association study.

BACKGROUND: Preterm birth (PTB) is a complex disorder associated with significant neonatal mortality and morbidity and long-term adverse health consequences. Multiple lines of evidence suggest that genetic factors play an important role in its etiology. This study was designed to identify genetic variation associated with PTB in oxytocin pathway genes whose role in parturition is well known. METHODS: To identify common genetic variants predisposing to PTB, we genotyped 16 single nucleotide polymorphisms (SNPs) in the oxytocin (OXT), oxytocin receptor (OXTR), and leucyl/cystinyl aminopeptidase (LNPEP) genes in 651 case infants from the U.S. and one or both of their parents. In addition, we examined the role of rare genetic variation in susceptibility to PTB by conducting direct sequence analysis of OXTR in 1394 cases and 1112 controls from the U.S., Argentina, Denmark, and Finland. This study was further extended to maternal triads (maternal grandparents-mother of a case infant, N=309). We also performed in vitro analysis of selected rare OXTR missense variants to evaluate their functional importance. RESULTS: Maternal genetic effect analysis of the SNP genotype data revealed four SNPs in LNPEP that show significant association with prematurity. In our case-control sequence analysis, we detected fourteen coding variants in exon 3 of OXTR, all but four of which were found in cases only. Of the fourteen variants, three were previously unreported novel rare variants. When the sequence data from the maternal triads were analyzed using the transmission disequilibrium test, two common missense SNPs (rs4686302 and rs237902) in OXTR showed suggestive association for three gestational age subgroups. In vitro functional assays showed a significant difference in ligand binding between wild-type and two mutant receptors. CONCLUSIONS: Our study suggests an association between maternal common polymorphisms in LNPEP and susceptibility to PTB. Maternal OXTR missense SNPs rs4686302 and rs237902 may have gestational age-dependent effects on prematurity. Most of the OXTR rare variants identified do not appear to significantly contribute to the risk of PTB, but those shown to affect receptor function in our in vitro study warrant further investigation. Future studies with larger sample sizes are needed to confirm the findings of this study.

Further analysis of the lens of ephrin-A5-/- mice: development of postnatal defects.

PURPOSE: The cells of the mammalian lens must be carefully organized and regulated to maintain clarity. Recent studies have identified the Eph receptor ligand ephrin-A5 as a major contributor to lens development, as mice lacking ephrin-A5 develop abnormal lenses, resulting in cataracts. As a follow-up to our previous study on the cataracts observed in ephrin-A5(-/-) animals, we have further examined the morphological and molecular changes in the ephrin-A5(-/-) lens. METHODS: Wild-type and ephrin-A5(-/-) eyes at various ages were fixed, sectioned, and examined using histological techniques. Protein expression and localization were determined using immunohistochemistry and western blot analysis. RESULTS: Lens abnormalities in the ephrin-A5(-/-) animals are observed at postnatal stages, with lens opacity occurring by postnatal day 21. Structural defects in the lens are first observed in the outer lens fiber cell region where cells in the ephrin-A5(-/-) lens are severely disorganized. Ephrin-A5 and the Eph receptor EphA2 are expressed during early ocular development and continue to be expressed into postnatal stages. The cataracts in the ephrin-A5(-/-) mutants occur regardless of the presence of the CP49 mutation. CONCLUSIONS: In this follow-up study, we have uncovered additional details explicating the mechanisms underlying ephrin-A5 function in the lens. Furthermore, elucidation of the expression of ephrin-A5 and the Eph receptor EphA2 in the lens supports a fundamental role for this receptor-ligand complex in lens development. These observations, in concert with our previous study, strongly suggest that ephrin-A5 has a critical role in postnatal lens fiber organization to maintain lens transparency.

Search for genetic modifiers of IRF6 and genotype-phenotype correlations in Van der Woude and popliteal pterygium syndromes.

Van der Woude syndrome is the most common form of syndromic orofacial clefting, accounting for 1-2% of all patients with cleft lip and/or cleft palate. Van der Woude and popliteal pterygium syndromes are caused by mutations in IRF6, but phenotypic variability within and among families with either syndrome suggests that other genetic factors contribute to the phenotypes. The aim of this study was to identify common variants acting as genetic modifiers of IRF6 as well as genotype-phenotype correlations based on mutation type and location. We identified an association between mutations in the DNA-binding domain of IRF6 and limb defects (including pterygia). Although we did not detect formally significant associations with the genes tested, borderline associations suggest several genes that could modify the VWS phenotype, including FOXE1, TGFB3, and TFAP2A. Some of these genes are hypothesized to be part of the IRF6 gene regulatory network and may suggest additional genes for future study when larger sample sizes are also available. We also show that families with the Van de Woude phenotype but in whom no mutations have been identified have a lower frequency of cleft lip, suggesting there may be locus and/or mutation class differences in Van de Woude syndrome.

Replication of genome wide association identified candidate genes confirm the role of common and rare variants in PAX7 and VAX1 in the etiology of nonsyndromic CL(P).

Following recent genome wide association studies (GWAS), significant genetic associations have been identified for several genes with nonsyndromic cleft lip with or without cleft palate (CL(P)). To replicate two of these GWAS signals, we investigated the role of common and rare variants in the PAX7 and VAX1 genes. TaqMan genotyping was carried out for SNPs in VAX1 and PAX7 and transmission disequilibrium test (TDT) was performed to test for linkage and association in each population. Direct sequencing in and around the PAX7 and VAX1 genes in 1,326 individuals of European and Asian ancestry was done. The TDT analysis showed strong associations with markers in VAX1 (rs7078160, P = 2.7E-06 and rs475202, P = 0.0002) in a combined sample of Mongolian and Japanese CL(P) case-parent triads. Analyses using parent-of-origin effects showed significant excess transmission of the minor allele from both parents with the effect in the mothers (P = 6.5E-05, OR (transmission) = 1.91) more striking than in the fathers (P = 0.004, OR (transmission) = 1.67) for VAX1 marker rs7078160 in the combined Mongolian and Japanese samples when all cleft types were combined. The rs6659735 trinucleotide marker in PAX7 was significantly associated with all the US cleft groups combined (P = 0.007 in all clefts and P = 0.02 in CL(P)). Eight rare missense mutations found in PAX7 and two rare missense mutations in VAX1. Our study replicated previous GWAS findings for markers in VAX1 in the Asian population, and identified rare variants in PAX7 and VAX1 that may contribute to the etiology of CL(P). Determining the role of rare variants clearly warrants further investigation.

Candidate gene linkage approach to identify DNA variants that predispose to preterm birth.

BACKGROUND: The aim of this study was to identify genetic variants contributing to preterm birth (PTB) using a linkage candidate gene approach. METHODS: We studied 99 single-nucleotide polymorphisms (SNPs) for 33 genes in 257 families with PTBs segregating. Nonparametric and parametric analyses were used. Premature infants and mothers of premature infants were defined as affected cases in independent analyses. RESULTS: Analyses with the infant as the case identified two genes with evidence of linkage: CRHR1 (P = 0.0012) and CYP2E1 (P = 0.0011). Analyses with the mother as the case identified four genes with evidence of linkage: ENPP1 (P = 0.003), IGFBP3 (P = 0.006), DHCR7 (P = 0.009), and TRAF2 (P = 0.01). DNA sequence analysis of the coding exons and splice sites for CRHR1 and TRAF2 identified no new likely etiologic variants. CONCLUSION: These findings suggest the involvement of six genes acting through the infant and/or the mother in the etiology of PTB.

Analysis of PAC1 receptor gene variants in Caucasian and African American infants dying of sudden infant death syndrome.

AIM: Stress peptide, pituitary adenylate cyclase-activating polypeptide (PACAP), has been implicated in sudden infant death syndrome (SIDS). The aim of this exploratory study was to determine whether variants in the gene encoding the PACAP-specific receptor, PAC1, are associated with SIDS in Caucasian and African American infants. METHODS: Polymerase chain reaction and Sanger DNA sequencing was used to compare variants in the 5'-untranslated region, exons and intron-exon boundaries of the PAC1 gene in 96 SIDS cases and 96 race- and gender-matched controls. RESULTS: The intron 3 variant, A/G: rs758995 (variant 'h'), and the intron 6 variant, C/T: rs10081254 (variant 'n'), were significantly associated with SIDS in Caucasians and African Americans, respectively (p < 0.05). Also associated with SIDS were interactions between the variants rs2302475 (variant 'i') in PAC1 and rs8192597 and rs2856966 in PACAP among Caucasians (p < 0.02) and rs2267734 (variant 'q') in PAC1 and rs1893154 in PACAP among African Americans (p < 0.01). However, none of these differences survived post hoc analysis. CONCLUSION: Overall, this study does not support a strong association between variants in the PAC1 gene and SIDS; however, a number of potential associations between race-specific variants and SIDS were identified that warrant targeted investigations in future studies.