Integrative Review of Genetic Factors Influencing Neurodevelopmental Outcomes in Preterm Infants

Innovative computational approaches shed light on genetic mechanisms underlying cognitive impairment among children born extremely preterm

BACKGROUND

Although survival rates for infants born extremely preterm (gestation < 28 weeks) have improved significantly in recent decades, neurodevelopmental impairment remains a major concern. Children born extremely preterm remain at high risk for cognitive impairment from early childhood to adulthood. However, there is limited evidence on genetic factors associated with cognitive impairment in this population.

METHODS

First, we used a latent profile analysis (LPA) approach to characterize neurocognitive function at age 10 for children born extremely preterm. Children were classified into two groups: (1) no or low cognitive impairment, and (2) moderate-to-severe cognitive impairment. Second, we performed TOPMed-based genotype imputation on samples with genotype array data (n = 528). Third, we then conducted a genome-wide association study (GWAS) for LPA-inferred cognitive impairment. Finally, computational analysis was conducted to explore potential mechanisms underlying the variant x LPA association.

RESULTS

We identified two loci reaching genome-wide significance (p value < 5e-8): TEA domain transcription factor 4 (TEAD4 at rs11829294, p value = 2.40e-8) and syntaxin 18 (STX18 at rs79453226, p value = 1.91e-8). Integrative analysis with brain expression quantitative trait loci (eQTL), chromatin conformation, and epigenomic annotations suggests tetraspanin 9 (TSPAN9) and protein arginine methyltransferase 8 (PRMT8) as potential functional genes underlying the GWAS signal at the TEAD4 locus.

CONCLUSIONS

We conducted a novel computational analysis by utilizing an LPA-inferred phenotype with genetics data for the first time. This study suggests that rs11829294 and its LD buddies have potential regulatory roles on genes that could impact neurocognitive impairment for extreme preterm born children.

Abnormal placental DNA methylation variation in spontaneous preterm birth

OBJECTIVE

Preterm birth (PTB) has become a major public health concern as the leading cause of neonatal death, but little is understood about its etiology. Children born preterm are also at increased risk of long-term consequences such as neurodevelopmental disorders, adulthood hypertension and diabetes. Recent studies have indicated that DNA methylation may be involved in the occurrence of PTB as well as related adverse outcomes. The latest Infinium EPIC BeadChip extends the coverage of the genome and provides a better tool to help investigate the involvement of DNA methylation in these conditions.

METHODS

We conducted this case-control study in three Women and Children's hospitals in South China, and enrolled 32 spontaneous preterm births and 16 term births. We assessed placental DNA methylation profiling of these participants with the Infinium EPIC BeadChip. We identified PTB and gestational age (GA)-associated CpG sites with limma regression model, and applied seqlm to identify PTB-associated regions. We performed gene ontology analysis to further interpret functional enrichment of the identified differentially methylated genes in PTB.

RESULTS

We identified a total of 8 differentially methylated positions (DMPs) that were significantly associated with PTB (FDR < 0.1) and a total of 15 DMPs that were associated with GA (FDR < 0.1). In the regional analysis, one differentially methylated region in the SLC23A1 gene overlapped with PTB-associated CpG site. The differentially methylated CpG sites in PTB were mapped to the genes involving in biological processes mainly regarding neurodevelopment, regulation of inflammation and metabolism.

CONCLUSION

Our findings suggested that preterm placenta have distinct DNA methylation alterations, and these alteration patterns established at birth provide insight into the long-term consequences of preterm birth.

Genetic Risk Factors for Poor Cognitive Development in Children With Low Birth Weight

Low birth weight is an ongoing public health problem with severe consequences for those affected, including early morbidity and mortality and elevated risk for lifelong deficits in cognitive function. These deficits can be ameliorated by early intervention in many cases. To contribute to criteria for earlier identification of at-risk children prior to the onset of delays or deficits, we examined relationships between three gene candidates-SLC6A4, BDNF, COMT-and cognitive outcomes at school age in a secondary analysis of existing data from a nationally representative cohort. Single nucleotide polymorphism rs4074134, a variant of BDNF, and a rare insertion/deletion in the intron region of SLC6A4 were significant predictors of cognitive performance. Our final model predicted 17% of the variance in composite cognitive test scores among children with low birth weight at school age (F = 96.36, p < .001, R2 = .17). Specifically, children homozygous for cytosine at rs4074134 scored .62 standard deviations higher on a measure of global cognition than children with one or more thymine. Similarly, children with an extra-long copy number variant of SLC6A4 scored .88 standard deviations higher than children who had one or more short forms of the gene. These findings support the potential for an approach to identifying children with low birth weights who are most at need of early intervention services. Future research should focus on validation of these findings in an independent sample and confirmation of the biological mechanisms through which these genes influence cognitive development.

Interaction Between Prematurity and the MAOA Gene on Mental Development in Children: A Longitudinal View

This study aimed to examine the association of dopamine-related genes with mental and motor development and the gene-environment interaction in preterm and term children. A total of 201 preterm and 111 term children were examined for their development at 6, 12, 18, 24, and 36 months and were genotyped for 15 single-nucleotide polymorphisms (SNPs) in dopamine-related genes (DRD2, DRD3, DAT1, COMT, and MAOA). An independent sample of 256 preterm children was used for replication. Since the developmental age trends of preterm children differed from those of term children, the analyses were stratified by prematurity. Among the 8 SNPs on the MAOA gene examined in the whole learning sample, the results of linkage disequilibrium analysis indicated that they were located in one block (all D' > 0.9), and rs2239448 was chosen as the tag (r² > 0.85). In the analysis of individual SNPs in each dopamine-related gene, the tag SNP (rs2239448) in MAOA remained significantly associated with the mental scores of preterm children for the interaction with age trend (p < 0.0001; largest effect size of 0.65 at 24 months) after Bonferroni correction for multiple testing. Similar findings for rs2239448 were replicated in the independent sample (p = 0.026). However, none of the SNPs were associated with the motor scores of preterm children, and none were related to the mental or motor scores of term children. The genetic variants of the MAOA gene exert influence on mental development throughout early childhood for preterm, but not term, children.

Sleep and prematurity: sleep outcomes in preterm children and influencing factors

BACKGROUND

Sleep undergoes changes from birth to adulthood, while sleep disorders are associated with various cognitive deficiencies in childhood. In parallel, prematurity is known to predispose to poor neurodevelopmental outcomes. Our aim is to provide literature data about factors influencing sleep in the premature infants and sleep outcomes in this population.

METHODS

A systematic review was conducted using a variety of health-related databases. Original research papers were considered and no year-of-publication restriction was placed.

RESULTS

In total, 22 articles fulfilled our selection criteria. Available studies present remarkable heterogeneity in terms of methodological design. Compared to full term, premature infants exhibit significant differences in sleep structure, which mainly include differences in electroencephalographic spectral values, in total sleep time and in arousal threshold. Furthermore, prematurity seems to be a risk factor of sleep breathing disorders in childhood and adolescence. Data about the effect of methylxanthines and the environment of neonatal intensive care unit is controversial. With regard to the impact of prematurity-related sleep disorders on future neurodevelopment, available research papers are generally few.

CONCLUSIONS

The alterations in sleep patterns are an outcome of prematurity (immaturity of nervous system) as well as of postnatal factors and comorbidities. Sleep problems in this population of infants seems to be a missing piece of the puzzle of impaired neurodevelopment. Future studies should focus on interventions to improve sleep hygiene and limit neurodevelopmental problems.

Neurocognitive Outcome After Treatment With(out) ECMO for Neonatal Critical Respiratory or Cardiac Failure

Over the years, it has become clear that children growing up after neonatal critical illness are at high risk of long-term neurocognitive deficits that impact their school performance and daily life activities. Although the pathophysiological mechanisms remain largely unknown, emerging evidence seems to suggest that long-term neuropsychological deficits following neonatal critical illness are not associated with the type of treatment, such as extracorporeal membrane oxygenation (ECMO), but rather with underlying disease processes. In this review, neurocognitive outcome and brain pathology following neonatal critical respiratory and cardiac illness, either treated with or without ECMO, are described and compared in order to gain insight into potential underlying pathophysiological mechanisms. Putting these findings together, it becomes apparent that both children with complex congenital heart disease and children who survived severe respiratory failure are at risk of neurocognitive deficits later in life. Neurorehabilitation strategies, such as Cogmed working-memory training, are discussed. While prevention of neurocognitive deficits altogether should be strived for in the future, this is not realistic at this moment. It is therefore of great importance that children growing up after neonatal critical illness receive long-term care that includes psychoeducation and personalized practical tools that can be used to improve their daily life activities.

Report of a workshop on research gaps in the treatment of cerebral palsy

Cerebral palsy (CP) is heterogeneous in etiology and manifestations, making research into relevant therapies difficult and limiting the generalizability of the results. We report here on the NIH CP symposium, where stakeholders from academic, clinical, regulatory, and advocacy backgrounds discussed the major challenges and needs for moving forward with clinical research in CP, and outlined priorities and action items. New information is constantly generated through research into pathogenesis and etiology. Clinical research and new therapeutic approaches need to keep pace, through large data registry integration and new research designs. Development of standardized data collection, increasing academic focus on CP research, and iterative approaches to treatment throughout the patients' lives, have all been identified as areas of focus. The workshop identified critical gaps and areas of focus to increase the evidence base for therapeutic approaches to determine which treatments work best for which patients in the near future. These include consolidation and optimization of databases and registries, updates to the research methodology, and better integration of resources and stakeholders.