Cerebral palsy and related neuromotor disorders: Overview of genetic and genomic studies

Cerebral palsy (CP) is a debilitating condition characterized by abnormal movement or posture, beginning early in development. Early family and twin studies and more recent genomic investigations clearly demonstrate that genetic factors of major effect contribute to the etiology of CP. Most copy number variants and small alterations of nucleotide sequence that cause CP arise as a result of de novo mutations, so studies that estimate heritability on basis of recurrence frequency within families substantially underestimate genetic contributions to the etiology. At least 4% of patients with typical CP have disease-causing CNVs, and at least 14% have disease-causing single nucleotide variants or indels. The rate of pathogenic genomic lesions is probably more than twice as high among patients who have atypical CP, i.e., neuromotor dysfunction with additional neurodevelopmental abnormalities or malformations, or with MRI findings and medical history that are not characteristic of a perinatal insult. Mutations of many different genetic loci can produce a CP-like phenotype. The importance of genetic variants of minor effect and of epigenetic modifications in producing a multifactorial predisposition to CP is less clear. Recognizing the specific cause of CP in an affected individual is essential to providing optimal clinical management. An etiological diagnosis provides families an "enhanced compass" that improves overall well-being, facilitates access to educational and social services, permits accurate genetic counseling, and, for a subset of patients such as those with underlying inherited metabolic disorders, may make precision therapy that targets the pathophysiology available. Trio exome sequencing with assessment of copy number or trio genome sequencing with bioinformatics analysis for single nucleotide variants, indels, and copy number variants is clinically indicated in the initial workup of CP patients, especially those with additional malformations or neurodevelopmental abnormalities.

The NESHIE and CP Genetics Resource (NCGR): A database of genes and variants reported in neonatal encephalopathy with suspected hypoxic ischemic encephalopathy (NESHIE) and consequential cerebral palsy (CP)

Neonatal encephalopathy (NE) with suspected hypoxic ischaemic encephalopathy (HIE) (NESHIE) is a complex syndrome occurring in newborns, characterised by altered neurological function. It has been suggested that genetic variants may influence NESHIE susceptibility and outcomes. Unlike NESHIE, for which a limited number of genetic studies have been performed, many studies have identified genetic variants associated with cerebral palsy (CP), which can develop from severe NESHIE. Identifying variants in patients with CP, as a consequence of NESHIE, may provide a starting point for the identification of genetic variants associated with NESHIE outcomes. We have constructed NCGR (NESHIE and CP Genetics Resource), a database of genes and variants reported in patients with NESHIE and CP (where relevant to NESHIE), for the purpose of collating and comparing genetic findings between the two conditions. In this paper we describe the construction and functionality of NCGR. Furthermore, we demonstrate how NCGR can be used to prioritise genes and variants of potential clinical relevance that may underlie a genetic predisposition to NESHIE and contribute to an understanding of its pathogenesis.

Gene-Environment Interactions During the First Thousand Days Influence Childhood Neurological Diagnosis

Gene-environment (G x E) interactions significantly influence neurologic outcomes. The maternal-placental-fetal (MPF) triad, neonate, or child less than 2 years may first exhibit significant brain disorders. Neuroplasticity during the first 1000 days will more likely result in life-long effects given critical periods of development. Developmental origins and life-course principles help recognize changing neurologic phenotypes across ages. Dual diagnostic approaches are discussed using representative case scenarios to highlight time-dependent G x E interactions that contribute to neurologic sequelae. Horizontal analyses identify clinically relevant phenotypic form and function at different ages. Vertical analyses integrate the approach using systems-biology from genetic through multi-organ system interactions during each developmental age to understand etiopathogenesis. The process of ontogenetic adaptation results in immediate or delayed positive and negative outcomes specific to the developmental niche, expressed either as a healthy child or one with neurologic sequelae. Maternal immune activation, ischemic placental disease, and fetal inflammatory response represent prenatal disease pathways that contribute to fetal brain injuries. These processes involve G x E interactions within the MPF triad, phenotypically expressed as fetal brain malformations or destructive injuries within the MPF triad. A neonatal minority express encephalopathy, seizures, stroke, and encephalopathy of prematurity as a continuum of trimester-specific G x E interactions. This group may later present with childhood sequelae. A healthy neonatal majority present at older ages with sequelae such as developmental disorders, epilepsy, mental health diseases, tumors, and neurodegenerative disease, often during the first 1000 days. Effective preventive, rescue, and reparative neuroprotective strategies require consideration of G x E interactions interplay over time. Addressing maternal and pediatric health disparities will maximize medical equity with positive global outcomes that reduce the burden of neurologic diseases across the lifespan.

Association of Infection in Neonates and Long-Term Neurodevelopmental Outcome

Perinatal and neonatal infection and associated inflammatory response may adversely affect brain development and lead to neurodevelopmental impairment. Factors that predict the risk of infection and subsequent adverse outcomes have been identified but substantial gaps remain in identifying mechanisms and interventions that can alter outcomes. This article describes the current epidemiology of neonatal sepsis, the pathogenesis of brain injury with sepsis, and the reported long-term neurodevelopment outcomes among survivors.

"The First Thousand Days" Define a Fetal/Neonatal Neurology Program

Gene-environment interactions begin at conception to influence maternal/placental/fetal triads, neonates, and children with short- and long-term effects on brain development. Life-long developmental neuroplasticity more likely results during critical/sensitive periods of brain maturation over these first 1,000 days. A fetal/neonatal program (FNNP) applying this perspective better identifies trimester-specific mechanisms affecting the maternal/placental/fetal (MPF) triad, expressed as brain malformations and destructive lesions. Maladaptive MPF triad interactions impair progenitor neuronal/glial populations within transient embryonic/fetal brain structures by processes such as maternal immune activation. Destructive fetal brain lesions later in pregnancy result from ischemic placental syndromes associated with the great obstetrical syndromes. Trimester-specific MPF triad diseases may negatively impact labor and delivery outcomes. Neonatal neurocritical care addresses the symptomatic minority who express the great neonatal neurological syndromes: encephalopathy, seizures, stroke, and encephalopathy of prematurity. The asymptomatic majority present with neurologic disorders before 2 years of age without prior detection. The developmental principle of ontogenetic adaptation helps guide the diagnostic process during the first 1,000 days to identify more phenotypes using systems-biology analyses. This strategy will foster innovative interdisciplinary diagnostic/therapeutic pathways, educational curricula, and research agenda among multiple FNNP. Effective early-life diagnostic/therapeutic programs will help reduce neurologic disease burden across the lifespan and successive generations.

The Association Study of IL-23R Polymorphisms With Cerebral Palsy in Chinese Population

Background: Cerebral palsy (CP) is a syndrome of non-progressive motor dysfunction caused by early brain development injury. Recent evidence has shown that immunological abnormalities are associated with an increased risk of CP.

Methods: We recruited 782 children with CP as the case group and 770 healthy children as the control group. The association between IL-23R single nucleotide polymorphisms (SNPs; namely, rs10889657, rs6682925, rs1884444, rs17375018, rs1004819, rs11805303, and rs10889677) and CP was studied by using a case–control method and SHEsis online software. Subgroup analysis based on complications and clinical subtypes was also carried out.

Results: There were differences in the allele and genotype frequencies between CP cases and controls at the rs11805303 and rs10889677 SNPs (Pallele = 0.014 and 0.048, respectively; Pgenotype = 0.023 and 0.008, respectively), and the difference in genotype frequency of rs10889677 remained significant after Bonferroni correction (Pgenotype = 0.048). Subgroup analysis revealed a more significant association of rs10889677 with CP accompanied by global developmental delay (Pgenotype = 0.024 after correction) and neonatal encephalopathy (Pgenotype = 0.024 after correction).

Conclusion: The present results showed a significant association between IL-23R and CP, suggesting that IL-23R may play a potential role in CP pathogenesis.

Neurologic outcome after fetal inflammatory response syndrome: Trimester-specific considerations

Clinical signs and neuroimaging patterns associated with the fetal inflammatory response syndrome (FIRS) worsen or mimic the clinical repertoire after intrapartum hypoxic-ischemic encephalopathy (HIE) during labor and/or parturition. Diagnostic considerations expressed as neonatal encephalopathy (NE) must consider chronic as well as acute factors associated with FIRS. Trimester-specific factors adversely alter the interactions of the maternal/placental/fetal (MPF) triad and influence the postnatal phenotype of FIRS. Anticipatory guidance for families by clinicians caring for survivors with FIRS, as well as researchers, must consider acute and chronic effects that influence neurologic outcome. Novel neurotherapeutic interventions must include prenatal preventive as well as peripartum/postnatal rescue and repair strategies to effectively reduce the presence and severity of sequelae from FIRS.

Association of neonatal inflammatory markers and perinatal stroke subtypes

OBJECTIVE

To examine the relationship between neonatal inflammatory cytokines and perinatal stroke using a systems biology approach analyzing serum and blood-spot cytokines from 47 patients.

METHODS

This was a population-based, controlled cohort study with prospective and retrospective case ascertainment. Participants were recruited through the Alberta Perinatal Stroke Project. Stroke was classified as neonatal arterial ischemic stroke (NAIS), arterial presumed perinatal ischemic stroke (APPIS), or periventricular venous infarction (PVI). Biosamples were stored blood spots (retrospective) and acute serum (prospective). Controls had comparable gestational and maternal ages. Sixty-five cytokines were measured (Luminex). Hierarchical clustering analysis was performed to create heat maps. The Fisher linear discriminant analysis was used to create projection models to determine discriminatory boundaries between stroke types and controls.

RESULTS

A total of 197 participants were analyzed (27 with NAIS, 8 with APPIS, 12 with PVI, 150 controls). Cytokines were quantifiable with quality control measures satisfied (standards testing, decay analysis). Linear discriminant analysis had high accuracy in using cytokine profiles to separate groups. Profiles in participants with PVI and controls were similar. NAIS separation was accurate (sensitivity 77%, specificity 97%). APPIS mapping was also distinguishable from NAIS (sensitivity 86%, specificity 99%). Classification tree analysis generated similar diagnostic accuracy.

CONCLUSIONS

Unique inflammatory biomarker signatures are associated with specific perinatal stroke diseases. Findings support an acquired pathophysiology and suggest the possibility that at-risk pregnancies might be identified to develop prevention strategies.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that differences in acute neonatal serum cytokine profiles can discriminate between patients with specific perinatal stroke diseases and controls.

Sex-Specific Genetic Susceptibility to Adverse Neurodevelopmental Outcome in Offspring of Pregnancies at Risk of Early Preterm Delivery

OBJECTIVE

To evaluate sex-specific genetic susceptibility to adverse neurodevelopmental outcome (ANO, defined as cerebral palsy [CP], mental, or psychomotor delay) at risk for early preterm birth (EPTB, < 32 weeks).

STUDY DESIGN

Secondary case-control analysis of a trial of magnesium sulfate (MgSO4) before anticipated EPTB for CP prevention. Cases are infants who died by the age of 1 year or developed ANO. Controls, matched by maternal race and infant sex, were neurodevelopmentally normal survivors. Neonatal DNA was evaluated for 80 polymorphisms in inflammation, coagulation, vasoregulation, excitotoxicity, and oxidative stress pathways using Taqman assays. The primary outcome for this analysis was sex-specific ANO susceptibility. Conditional logistic regression estimated each polymorphism's odds ratio (OR) by sex stratum, adjusting for gestational age, maternal education, and MgSO4-corticosteroid exposures. Holm-Bonferroni corrections, adjusting for multiple comparisons (p < 7.3 × 10-4), accounted for linkage disequilibrium between markers.

RESULTS

Analysis included 211 cases (134 males; 77 females) and 213 controls (130 males; 83 females). An interleukin-6 (IL6) polymorphism (rs2069840) was associated with ANO in females (OR: 2.6, 95% confidence interval [CI]: 1.5-4.7; p = 0.001), but not in males (OR: 0.8, 95% CI: 0.5-1.2; p = 0.33). The sex-specific effect difference was significant (p = 7.0 × 10-4) and was unaffected by MgSO4 exposure. No other gene-sex associations were significant.

CONCLUSION

An IL6 gene locus may confer susceptibility to ANO in females, but not males, after EPTB.

Neonatal Brain Injury and Genetic Causes of Adult-Onset Neurodegenerative Disease in Mice Interact With Effects on Acute and Late Outcomes

Neonatal brain damage and age-related neurodegenerative disease share many common mechanisms of injury involving mitochondriopathy, oxidative stress, excitotoxicity, inflammation, and neuronal cell death. We hypothesized that genes causing adult-onset neurodegeneration can influence acute outcome after CNS injury at immaturity and on the subsequent development of chronic disability after early-life brain injury. In two different transgenic (Tg) mouse models of adult-onset neurodegenerative disease, a human A53T-α-synuclein (hαSyn) model of Parkinson's disease (PD) and a human G93A-superoxide dismutase-1(hSOD1) model of amyotrophic lateral sclerosis (ALS), mortality and survivor morbidity were significantly greater than non-Tg mice and a Tg mouse model of Alzheimer's disease after neonatal traumatic brain injury (TBI). Acutely after brain injury, hαSyn neonatal mice showed a marked enhancement of protein oxidative damage in forebrain, brain regional mitochondrial oxidative metabolism, and mitochondriopathy. Extreme protein oxidative damage was also observed in neonatal mutant SOD1 mice after TBI. At 1 month of age, neuropathology in forebrain, midbrain, and brainstem of hαSyn mice with neonatal TBI was greater compared to sham hαSyn mice. Surviving hαSyn mice with TBI showed increased hαSyn aggregation and nitration and developed adult-onset disease months sooner and died earlier than non-injured hαSyn mice. Surviving hSOD1 mice with TBI also developed adult-onset disease and died sooner than non-injured hSOD1 mice. We conclude that mutant genes causing PD and ALS in humans have significant impact on mortality and morbidity after early-life brain injury and on age-related disease onset and proteinopathy in mice. This study provides novel insight into genetic determinants of poor outcomes after acute injury to the neonatal brain and how early-life brain injury can influence adult-onset neurodegenerative disease during aging.

Dried blood spot compared to plasma measurements of blood-based biomarkers of brain injury in neonatal encephalopathy

BACKGROUND

Data correlating dried blood spots (DBS) and plasma concentrations for neonatal biomarkers of brain injury are lacking. We hypothesized that candidate biomarker levels determined from DBS can serve as a reliable surrogate for plasma levels.

METHODS

In the context of a phase II multi-center trial evaluating erythropoietin for neuroprotection in neonatal encephalopathy (NE), DBS were collected at enrollment ( < 24 h), day 2, 4, and 5. Plasma was collected with the first and last DBS. The relationship between paired DBS-plasma determinations of brain-specific proteins and cytokines was assessed by correlation and Bland-Altman analyses. For analytes with consistent DBS-plasma associations, DBS-derived biomarker levels were related to brain injury by MRI and 1-year outcomes.

RESULTS

We enrolled 50 newborns with NE. While S100B protein, tumor necrosis factor α, interleukin (IL)1 β, IL-6, IL-8 demonstrated significant DBS-plasma correlations, Bland-Altman plots demonstrated that the methods are not interchangeable, with a 2 to 4-fold error between measurements. No significant relationships were found between DBS levels of TNFα, IL-6, and IL-8 and outcomes.

CONCLUSION

Further work is needed to optimize elution and assay methods before using DBS specimens as a reliable surrogate for plasma levels of candidate brain injury biomarkers in NE.

Genetic Variation, Magnesium Sulfate Exposure, and Adverse Neurodevelopmental Outcomes Following Preterm Birth

OBJECTIVE

To evaluate the association of magnesium sulfate (MgSO4) exposure and candidate gene polymorphisms with adverse neurodevelopmental outcomes following preterm birth.

STUDY DESIGN

We performed a nested case-control analysis of a randomized trial of maternal MgSO4 before anticipated preterm birth for the prevention of cerebral palsy (CP). Cases were children who died within 1 year of life or were survivors with abnormal neurodevelopment at age 2 years. Controls were race- and sex-matched survivors with normal neurodevelopment. We analyzed 45 candidate gene polymorphisms in inflammation, coagulation, and vascular regulation pathways and their association with (1) psychomotor delay, (2) mental delay, (3) CP, and (4) combined outcome of death/CP. Logistic regression analyses, conditional on maternal race and child sex, and adjusted for treatment group, gestational age at birth and maternal education, were performed.

RESULTS

Four hundred and six subjects, 211 cases and 195 controls, were analyzed. The strongest association was for IL6R (rs 4601580) in which each additional copy of the minor allele was associated with an increased risk of psychomotor delay (adjusted odds ratio 3.3; 95% confidence interval, 1.7-6.5; p < 0.001).

CONCLUSION

Candidate gene polymorphisms are associated with death and adverse neurodevelopmental outcomes following preterm birth. MgSO4 may abrogate this genotype association for some loci.

No association of labor epidural analgesia with cerebral palsy in children

BACKGROUND

Some pregnant women avoid labor epidural analgesia because of their concerns about risk of cerebral palsy in children. Although it is believed that labor epidural does not contribute to cerebral palsy, to our knowledge no study has been published to specifically address this concern. We carried out a retrospective case-control study to investigate whether labor epidural analgesia is associated with cerebral palsy in children.

METHODS

This study used data that were collected and entered into the Geisinger electronic health records between January 2004 and January 2013. During this period, 20,929 children were born at Geisinger hospitals. Among them, 50 children were diagnosed with cerebral palsy, and 20 of those were born vaginally. Each of these 20 cerebral palsy children was matched with up to 5 non-cerebral palsy children born at the same hospitals in the same timeframe using propensity scoring methods. Analgesia was classified as epidural (including epidural or combined spinal and epidural) or non-epidural. Conditional logistic regression was used to compare the percentages of deliveries with each analgesia type between the cerebral palsy and non-cerebral palsy groups.

RESULTS

In the non-cerebral palsy group, the percentage of patients receiving labor epidural analgesia was 72 %, and in the cerebral palsy group the percentage was 45 %. There was no significant difference between non-cerebral palsy and cerebral palsy groups (odds ratio, 0.57; 95 % confidence interval, 0.14-2.24; p = 0.42).

CONCLUSION

We found no association between the use of labor epidural analgesia and the occurrence of cerebral palsy in children.

Sleep disorders in children with cerebral palsy and its correlation with sleep disturbance in primary caregivers and other associated factors

AIMS

To observe prevalence of sleep disturbance (SD) in cerebral palsy (CP) children in a specific age-group and its correlation with SD in primary caregivers and other associated factors.

MATERIALS AND METHODS

This was a prospective cross-sectional study. SD assessed using Sleep Disturbance Scale for Children (SDSC) in CP children and Pittsburgh Sleep Quality Index (PSQI) in caregivers. Fifty cases of clinically diagnosed CP [27 females, mean age: 107.9 ΁ 29.5 months (range: 78-180 months)] fulfilling criteria were included.

RESULTS

Eighteen (36%) children had pathological sleep total score (TS) and Disorders of Initiating and Maintaining Sleep (DIMS) was the commonest SD (n = 25, 50%). All primary caregivers were mothers. Twenty-five (50%) mothers had SD on PSQI scale. DIMS, Disorders of Excessive Somnolence (DES), and TS had significant correlation with PSQI (P < 0.05). Disorders of Arousal (DA) and TS had significant correlation with seizures (P < 0.05) in CP children. Bed-sharing had significant correlation with SD in caregivers (P < 0.001) but not with CP children. No significant correlation was observed between SD in CP and gross motor function (Gross Motor Function Classification System), use of orthoses, and dental caries.

INTERPRETATION

Children with CP have underreported significant SD, which negatively impacts caregiver's sleep also. Seizure disorders and medications contribute significantly to SD.

The association between sex-related interleukin-6 gene polymorphisms and the risk for cerebral palsy

BACKGROUND

The relationship between genetic factors and the development of cerebral palsy (CP) has recently attracted much attention. Polymorphisms in the genes encoding proinflammatory cytokines have been shown to be associated with susceptibility to perinatal brain injury and development of CP. Interleukin-6 (IL-6) is a proinflammatory cytokine that plays a pivotal role in neonatal brain injury, but conflicting results have been reported regarding the association between IL-6 single nucleotide polymorphisms (SNPs) and CP. The purpose of this study was to analyze IL-6 gene polymorphisms and protein expression and to explore the role of IL-6 in the Chinese CP population.

METHODS

A total of 753 healthy controls and 713 CP patients were studied to detect the presence of five SNPs (rs1800796, rs2069837, rs2066992, rs2069840, and rs10242595) in the IL-6 locus. Of these, 77 healthy controls and 87 CP patients were selected for measurement of plasma IL-6 by Luminex assay. The SHEsis program was used to analyze the genotyping data. For all comparisons; multiple testing on each individual SNP was corrected by the SNPSpD program.

RESULTS

There were no differences in allele or genotype frequencies between the overall CP patients and controls among the five genetic polymorphisms. However, subgroup analysis found significant sex-related differences in allele and genotype frequencies. Differences were found between spastic CP and controls in males for rs2069837; between CP with periventricular leukomalacia and controls in males for rs1800796 and rs2066992; and between term CP and controls in males for rs2069837. Plasma IL-6 levels were higher in CP patients than in the controls, and this difference was more robust in full-term male spastic CP patients. Furthermore, the genotype has an effect on IL-6 synthesis.

CONCLUSIONS

The influence of IL-6 gene polymorphisms on IL-6 synthesis and the susceptibility to CP is related to sex and gestational age.

Gene-environment interactions in severe intraventricular hemorrhage of preterm neonates

Intraventricular hemorrhage (IVH) of the preterm neonate is a complex developmental disorder, with contributions from both the environment and the genome. IVH, or hemorrhage into the germinal matrix of the developing brain with secondary periventricular infarction, occurs in that critical period of time before the 32nd to 33rd wk postconception and has been attributed to changes in cerebral blood flow to the immature germinal matrix microvasculature. Emerging data suggest that genes subserving coagulation, inflammatory, and vascular pathways and their interactions with environmental triggers may influence both the incidence and severity of cerebral injury and are the subject of this review. Polymorphisms in the Factor V Leiden gene are associated with the atypical timing of IVH, suggesting an as yet unknown environmental trigger. The methylenetetrahydrofolate reductase (MTHFR) variants render neonates more vulnerable to cerebral injury in the presence of perinatal hypoxia. The present study demonstrates that the MTHFR 677C>T polymorphism and low 5-min Apgar score additively increase the risk of IVH. Finally, review of published preclinical data suggests the stressors of delivery result in hemorrhage in the presence of mutations in collagen 4A1, a major structural protein of the developing cerebral vasculature. Maternal genetics and fetal environment may also play a role.

Sequencing of the IL6 gene in a case-control study of cerebral palsy in children

Background

Cerebral palsy (CP) is a group of nonprogressive disorders of movement and posture caused by abnormal development of, or damage to, motor control centers of the brain. A single nucleotide polymorphism (SNP), rs1800795, in the promoter region of the interleukin-6 (IL6) gene has been implicated in the pathogenesis of CP by mediating IL-6 protein levels in amniotic fluid and cord plasma and within brain lesions. This SNP has been associated with other neurological, vascular, and malignant processes as well, often as part of a haplotype block.

Methods

To refine the regional genetic association with CP, we sequenced (Sanger) the IL6 gene and part of the promoter region in 250 infants with CP and 305 controls.

Results

We identified a haplotype of 7 SNPs that includes rs1800795. In a recessive model of inheritance, the variant haplotype conferred greater risk (OR = 4.3, CI = [2.0-10.1], p = 0.00007) than did the lone variant at rs1800795 (OR = 2.5, CI = [1.4-4.6], p = 0.002). The risk haplotype contains one SNP (rs2069845, CI = [1.2-4.3], OR = 2.3, p = 0.009) that disrupts a methylation site.

Conclusions

The risk haplotype identified in this study overlaps with previously identified haplotypes that include additional promoter SNPs. A risk haplotype at the IL6 gene likely confers risk to CP, and perhaps other diseases, via a multi-factorial mechanism.

Autism spectrum disorder in children born preterm-role of exposure to perinatal inflammation

Autism Spectrum Disorder (ASD) is the collective term for neurodevelopmental disorders characterized by qualitative impairments in social interaction, communication, and a restricted range of activities and interests. Many countries, including Australia, have reported a dramatic increase in the number of diagnoses over the past three decades, with current prevalence of ASD at 1 in every 110 individuals (~1%). The potential role for an immune-mediated mechanism in ASD has been implicated by several studies, and some evidence suggests a potential link between prenatal infection-driven inflammation and subsequent development of ASD. Furthermore, a modest number of contemporary studies have reported a markedly increased prevalence of ASD in children born preterm, who are at highest risk of exposure to perinatal inflammation. However, the mechanisms that underpin the susceptibility to infection-driven inflammation during pregnancy and risk of preterm birth, and how these intersect with the subsequent development of ASD in the offspring, is not understood. This review aims to summarize and discuss the potential mechanisms and evidence for the role of prenatal infection on the central nervous system, and how it may increase the susceptibility for ASD pathogenesis in children born preterm.

Association of Interleukin 6 gene polymorphisms with genetic susceptibilities to spastic tetraplegia in males: a case-control study

BACKGROUND

Cerebral palsy (CP) is a group of non-progressive motor impairment and permanent disorders causing limitation of activity and abnormal posture. It may be caused by infection (such as chorioamnionitis), asphyxia or multiple genetic factors. The Interleukin 6 gene (IL6) was suggested to be involved in the susceptibilities to CP risk as a kind of proinflammatory cytokine.

OBJECTIVE

To explore the genetic association between the polymorphisms of the IL6 gene and CP in the Chinese population.

METHODS

A total of 542 CP patients and 483 healthy control children were recruited in this study to detect five single nucleotide polymorphisms (rs1800796, rs2069837, rs2066992, rs2069840, and rs10242595) in the IL6 locus. Genotyping of SNPs was performed by the MassArray platform-based genotyping approach. The SHEsis program was applied to analyze the genotyping data.

RESULTS

Of the five selected SNPs, no significant allelic and genotypic association was found between CP patients and controls. However, subgroup analysis found significant differences in allele frequencies between spastic tetraplegia in males compared with controls at rs1800796 (OR=1.39, P=0.033, P=0.099 after SNPSpD correction) and rs2069837 (OR=1.58, P=0.012, P=0.035 after SNPSpD correction). The frequencies of the C allele of rs1800796 and the A allele of rs2069837 were greater in males with spastic tetraplegia than in the controls. The two SNPs haplotype rs1800796 (G) - rs2069837 (G) were also associated with a decreased risk of spastic tetraplegia in males (OR=0.619, P=0.009, P=0.027 after Bonferroni correction).

CONCLUSION

Genetic variation of the IL6 gene may influence susceptibility to spastic tetraplegia in males and its role in cerebral palsy deserves further evaluation in a large-scale and well-designed study.

Perinatal immunoproteins predict the risk of cerebral palsy in preterm children

OBJECTIVE

To investigate whether blood cytokines during the perinatal period predict the risk of cerebral palsy (CP) in preterm infants.

METHODS

This prospective cohort study comprised 169 children born before 32 weeks of gestation. Cord blood was drawn at birth, and 109 cytokines were analyzed using microarrays. Eleven cytokines were further measured from both cord and peripheral blood on days 1 and 7. Cerebral palsy was confirmed at 5 years of age.

RESULTS

Cerebral palsy was diagnosed in 19 children. Five clusters of cord blood cytokines were scored using factor analysis. According to logistic regression analysis, the scores of factors 1 and 2 independently predicted the risk of CP. These cytokines included several growth factors and chemokines, and they all tended to be higher in children with CP than in children without CP. Inflammatory cytokine levels were associated with CP risk on days 1 and 7 after birth.

CONCLUSION

The high blood concentrations of various cytokines during the perinatal period may relate to CP, and these cytokines may influence the pathways leading to early insult in the central nervous system. The risk profile of inflammatory cytokines is different at birth than during the first week after birth.

Genetic risk factors for perinatal arterial ischemic stroke

The cause of perinatal arterial ischemic stroke is unknown in most cases. We explored whether genetic polymorphisms modify the risk of perinatal arterial ischemic stroke. In a population-based case-control study of 1997-2002 births at Kaiser Permanente Northern California, we identified 13 white infants with perinatal arterial ischemic stroke. Control subjects included 86 randomly selected white infants. We genotyped polymorphisms in nine genes involved in inflammation, thrombosis, or lipid metabolism previously linked with stroke, and compared genotype frequencies in case and control individuals. We tested several polymorphisms: tumor necrosis factor-α -308, interleukin-6, lymphotoxin A, factor V Leiden, methyltetrahydrofolate reductase 1298 and 667, prothrombin 20210, and apolipoprotein E ε2 and ε4 alleles. Patients with perinatal arterial ischemic stroke were more likely than control subjects to demonstrate at least one apolipoprotein E ε4 allele (54% vs 25%, P = 0.03). More patients with perinatal arterial ischemic stroke carried two ε4 alleles than did control subjects (15% vs 2%, P = 0.09), although this finding lacked statistical significance. Proinflammatory and prothrombotic polymorphisms were not associated with perinatal arterial ischemic stroke. The apolipoprotein E polymorphism may confer genetic susceptibility for perinatal arterial ischemic stroke. Larger population-based studies are required to confirm this finding.

Early life exposure to air pollution: how bad is it?

Increasing concentrations of air pollution have been shown to contribute to an enormity of adverse health outcomes worldwide, which have been observed in clinical, epidemiological, and animal studies as well as in vitro investigations. Recently, studies have shown that air pollution can affect the developing fetus via maternal exposure, resulting in preterm birth, low birth weight, growth restriction, and potentially adverse cardiovascular and respiratory outcomes. This review will provide a summary of the harmful effects of air pollution exposure on the developing fetus and infant, and suggest potential mechanisms to limit the exposure of pregnant mothers and infants to air pollution.

Interleukin-6 polymorphism and bronchopulmonary dysplasia risk in very low-birthweight infants

BACKGROUND

The aim of the present study was to evaluate the role of interleukin (IL)-6-634 polymorphism in neonatal disorders such as bronchopulmonary dysplasia (BPD) and periventricular leukomalacia (PVL) in very low-birthweight (VLBW) infants.

METHODS

This prospective cohort study included 202 infants (gestational age at birth, 23-34 weeks; birthweight, 500-1499 g). Genotypic analysis (polymerase chain reaction-restriction fragment length polymorphism) was performed with DNA extracted from whole-blood samples.

RESULTS

Genotype distribution (66.8% CC, 28.2% CG, 5.0% GG) was similar to that in the adult Japanese population. BPD occurred in 85 infants (42.1%) among 202 VLBW infants. The duration of O(2) therapy in infants with CG/GG genotypes was significantly longer than that in infants with the CC genotype (CG/GG vs CC: 40.3 ± 52.2 days vs 28.4 ± 32.6 days, P < 0.05), but the prevalence of BPD was not associated with the CG/GG genotype (CG/GG, 40.0%; CC, 46.3%, P= 0.24). Infants with CG/GG genotypes were more likely to have received postnatal corticosteroid therapy for BPD than those with the CC genotype (CG/GG vs CC: 20.9% vs 11.1%, P = 0.05). PVL occurred in six infants (3.0%). There was no significant difference in the prevalence of PVL among IL-6-634 polymorphisms (CG/GG, 3.0%; CC, 3.0%, P = 0.65).

CONCLUSIONS

IL-6-634 polymorphism is associated with duration of oxygen therapy in VLBW infants. This suggests that the IL-6-634 polymorphism G allele is an aggravating factor of BPD. IL-6-634 polymorphism is not associated with PVL.

Genetic factors that influence short-term neurodevelopmental outcome in term hypoxic-ischaemic encephalopathic neonates

It is difficult to predict outcome in neonates that experience perinatal hypoxic ischaemia. Morbidity and mortality may be affected by genetic factors that augment inflammatory and coagulative responses. This prospective study analysed the effects of proinflammatory cytokine gene polymorphisms (tumour necrosis factor-α [TNFA] 308G>A and interleukin-6 [IL6] 174G>C) and prothrombotic factor gene mutations (prothrombin G20210A, factor V Leiden G1691A and methylenetetra hydrofolate reductase [MTHFR] C677T) on the early neurological prognosis in 40 term hypoxic ischaemic encephalopathic neonates. There were significant relationships for Sarnat and Sarnat staging with electroencephalographic findings, transfontanelle ultrasound (US) results, early neonatal outcome and neurological morbidity. Genetic mutations in the prothrombotic proteins, the TNFA 308G>A polymorphism and the cerebrospinal fluid levels of TNF-α protein were not related to clinical stage, electroencephalography, transfontanelle US or neurological status at discharge or at postnatal months 6 and 12. The IL6 174GC genotype demonstrated a protective role, being significantly correlated with normal electroencephalography, transfontanelle US and normal neurological findings at discharge. In conclusion, the IL6 174GC gene polymorphism seems to play a role in determining the risk and/or severity of perinatal cerebral injury.

The role of cytokines and inflammatory cells in perinatal brain injury

Perinatal brain injury frequently complicates preterm birth and leads to significant long-term morbidity. Cytokines and inflammatory cells are mediators in the common pathways associated with perinatal brain injury induced by a variety of insults, such as hypoxic-ischemic injury, reperfusion injury, toxin-mediated injury, and infection. This paper examines our current knowledge regarding cytokine-related perinatal brain injury and specifically discusses strategies for attenuating cytokine-mediated brain damage.

Elevated concentrations of inflammation-related proteins in postnatal blood predict severe developmental delay at 2 years of age in extremely preterm infants

OBJECTIVE

To evaluate the hypothesis that elevated levels of inflammation-related proteins in early postnatal blood predict impaired mental and motor development in extremely preterm infants.

STUDY DESIGN

We measured concentrations of 25 inflammation-related proteins in blood collected on postnatal days 1, 7, and 14 from 939 infants born before 28 weeks gestation. An elevated level was defined as a concentration in the highest quartile for gestational age and day of blood collection. We identified impaired development at age 24 months using the Bayley Scales of Infant Development, Second Edition. The primary outcomes were scores on the Mental Scale or the Motor Scale of <55 (more than 3 SDs below the mean).

RESULTS

For 17 of the 25 inflammation-related proteins, 1 or more statistically significant associations (P<.01) was found between an elevated blood level of the protein and a developmental impairment. Elevations on multiple days were more often associated with developmental impairment than were elevations present for only 1 day. The highest number of predictive elevations was found in day-14 blood.

CONCLUSION

In extremely preterm infants, elevated levels of inflammation-related proteins in blood collected on postnatal days 7 and 14, especially when sustained, are associated with impaired mental and motor development at age 2 years.

Fetal and maternal candidate single nucleotide polymorphism associations with cerebral palsy: a case-control study

OBJECTIVE

Previous studies have suggested associations between certain genetic variants and susceptibility to cerebral palsy (CP). This study was designed to assess established and novel maternal and child genetic and epidemiologic risk factors for CP along with their interactions.

METHODS

DNA from 587 case and 1154 control mother-child pairs was analyzed. A panel of 35 candidate single nucleotide polymorphisms (SNPs) were examined and included SNPs in genes associated with (1) thrombophilia, (2) inflammation, and (3) risk factors for CP (eg, preterm birth). Comparisons were specified a priori and made by using a χ(2) test.

RESULTS

There were 40 fetal and 28 maternal associations with CP when analyzed by CP subtype, gestational age, genotypes of apolipoprotein E, and haplotypes of mannose-binding-lectin. After Bonferroni correction for multiple testing, no fetal or maternal candidate SNP was associated with CP or its subtypes. Only fetal carriage of prothrombin gene mutation remained marginally associated with hemiplegia in term infants born to mothers with a reported infection during pregnancy. Odds ratio directions of fetal SNP associations were compared with previously reported studies and confirmed no trend toward association.

CONCLUSIONS

Except for the prothrombin gene mutation, individual maternal and fetal SNPs in our candidate panel were not found to be associated with CP outcome. Past reported SNP associations with CP were not confirmed, possibly reflecting type I error from small numbers and multiple testing in the original reports.

Proteomics/diagnosis of chorioamnionitis and of relationships with the fetal exposome

Proteomics, a relatively young science, originally emerged as a complement to genomics research. By definition, the goal of proteomics is to provide a snapshot of all the proteins within an organism, tissue or biological sample at a given moment. Proteomics has the ability to single out one or more proteins (biomarkers) that change consistently in affected subjects as compared to those disease-free. From a proteomics perspective, chorioamnionitis poses both challenges and opportunities. Challenges relate to the dynamic course of the inflammatory process, and compartmentalization of the gestational sac in relation to the maternal compartment. An inability to evaluate the amniotic fluid non-invasively and repeatedly for meaningful changes in its proteome, and lack of a true gold standard for diagnosis of inflammation and/or infection, represent additional challenges. On the other hand, the unbiased and holistic nature of proteomics offers a real opportunity to improve the current diagnostic and prognostic algorithms for chorioamnionitis. Even at this current stage there are reasons to believe that proteomic biomarkers will improve the understanding of how chorioamnionitis programs or affects the fetus in utero, thus defining its exposome (sum of interactions between genetic make-up of the fetus and the intrauterine environment) of pregnancies affected by infection and/or inflammation. This review summarizes the results of proteomics studies that have aimed or reached these goals.

Candidate genes and risk for CP: a population-based study

Studies suggest that genetic polymorphisms may increase an individual's susceptibility to CP. Most findings have yet to be corroborated in an independent cohort. This case-control study is nested within all 334,333 infants ≥36 wk gestation born at Kaiser Permanente Medical Care Program, 1991-2002. We included only non-Hispanic whites who had a neonatal blood sample available. Case patients (n = 138) were identified from medical records to have spastic or dyskinetic CP. Controls (n = 165) were randomly selected from the population. We genotyped polymorphisms previously associated with CP: inducible NOS (iNOS)-231, apolipoprotein E (apoE) ε2 and ε4 alleles, TNF-α-308, IL-8 -251, lymphotoxin 60, endothelial NOS -922, endothelial protein C receptor 219, mannose-binding lectin 54 and 52, factor V Leiden, methyltetrahydrofolate reductase 1298 and 667, prothrombin 20210, and platelet activator inhibitor 11053. Similar to previous reports, the iNOS-231 T allele (25.7 versus 18.9%, p = 0.04) and the apoE ε4 allele (19.3 versus 13.2%, p = 0.04) were more common in patients with CP than in controls. However, there was no statistically significant association between any genetic polymorphism and CP after correction for multiple comparisons.

Opposite effect of inflammation on subventricular zone versus hippocampal precursors in brain injury

OBJECTIVE

Inflammation promotes epidermal wound healing but is considered detrimental to recovery from central nervous system injury. Sick infants have increased levels of cytokines in their cerebrospinal fluid that correlate with poor neurological outcome. In this study, we investigated the role of neuroinflammation and more specifically interleukin 6 (IL-6) in the amplification of subventricular zone (SVZ) and subgranular zone (SGZ) neural precursors after neonatal brain injury.

METHODS

Neonatal hypoxia/ischemia (H/I) was induced in P6 rat pups, and IL-6 was quantified with or without indomethacin administration. Neural precursor responses were evaluated by neurosphere assays as well as by stereological analyses. Studies were performed to determine how IL-6 and leukemia-inhibiting factor (LIF) affect SVZ cell expansion, proliferation, and self-renewal.

RESULTS

Consistent with earlier studies, medially situated SVZ cells expanded after H/I. Contrary to our expectations, indomethacin significantly decreased both the initial reactive increase in these precursors and their ability to self-renew. By contrast, indomethacin increased proliferation in the SGZ and lateral SVZ. Indomethacin diminished the accumulation of microglia/macrophages and IL-6 production after H/I. In vitro IL-6 enhanced neurosphere growth, self-renewal, and tripotentiality and was more effective than LIF in promoting self-renewal. Enhanced precursor self-renewal also was obtained using prostaglandin E2, which is downstream of cyclooxygenase 2 and a target of indomethacin.

INTERPRETATION

These data implicate neuroinflammation and in particular IL-6 as a positive effector of primitive neural precursor expansion after neonatal brain injury. These findings have important clinical implications, as indomethacin and other anti-inflammatory agents are administered to premature infants for a variety of reasons.

Impact of histological chorioamnionitis, funisitis and clinical chorioamnionitis on neurodevelopmental outcome of preterm infants

BACKGROUND

The role of chorioamnionitis in neurodevelopment of preterm infants is not fully understood.

AIM

To examine the association between different indicators of intrauterine inflammation (clinical chorioamnionitis, histological chorioamnionitis and funisitis) and neurodevelopmental impairment in very preterm infants.

METHODS

Preterm infants with a birth weight of <1500 g or a gestational age of <32 weeks were included. Follow-up evaluation up to 2 years of age consisted of neurological examination, neurodevelopmental assessment and visual and audiologic tests. Outcome data were compared between the chorioamnionitis and the control groups, controlling for gestational age, birth weight and Apgar score at 5 min.

RESULTS

One hundred seventy-seven patients comprised the study population (mean gestational age 29±2 weeks, mean birth weight 1167±344 g). Histological chorioamnionitis was present in 49% of placentas, whereas funisitis was observed in 25%. In 57% cases clinical maternal chorioamnionitis was suspected. Follow-up was available for 130 (82%) patients. Infants with funisitis, compared with controls, had a significantly higher incidence of moderate to severe disability (18% vs 5%, OR 4.07; 95% CI 1.10-15.09).

CONCLUSION

The results of this study suggest that, unlike a broad definition of histological chorioamnionitis including inflammation of maternal or fetal placental tissues, funisitis may entail a higher risk of moderate to severe disability at 2 years of age in preterm infants.

The association of genetic polymorphisms with cerebral palsy: a meta-analysis

AIM

The aim of our meta-analysis was to summarize quantitatively the association of genetic polymorphisms with cerebral palsy (CP).

METHOD

We identified 16 studies on the association of genetic polymorphisms with CP in Pubmed, Elsevier Science Direct, Chinese Biomedical Literature Database, Chinese National Knowledge Infrastructure, and Wanfang. Eleven of these studies (involving a total of 2533 cases and 4432 controls) were used in the current meta-analysis. A study was included if (1) it was published up to September 2010 and (2) it was a case-control study. We excluded one study of family members because the analysis was based on linkage considerations. Meta odds ratios and 95% confidence intervals based on fixed-effects models or random-effects models were dependent on Cochran's Q statistic. We examined the relationship between alleles, as well as genotypes and susceptibility to CP.

RESULTS

Meta-analysis was performed for 17 genetic polymorphisms: apolipoprotein E (ε2,ε3,ε4), methylenetetrahydrofolate reductase (MTHFR) (rs1801133), coagulation factor II (rs1799963]), coagulation factor V (rs6025), coagulation factor VII (rs5742910/rs6046), interleukin-6 (IL-6) (rs1800795), endothelial nitric oxide (rs1800779/rs1799983/rs3918226), fibrinogen β-polypeptide (rs1800790), plasminogen activator inhibitor 1 (rs1799768/rs7242), TNF-β lymphotoxin α precursor (rs1041981), adducin 1 (α) (rs4961), ADRB2 (rs1042714), and tumour necrosis factor α (rs1800629). We found a significant association between CP and IL-6 (rs1800795) [C vs G: odds ratio (OR) 1.79, 95% confidence interval (CI) 1.44-2.22, p<0.001; CC+GC vs GG: OR 1.72, 95% CI 1.29-2.29, p=0.002; CC vs GG+GC: OR 2.17, 95% CI 1.52-3.09, p<0.001], but no other genetic polymorphisms.

INTERPRETATION

This meta-analysis demonstrated that CP is associated with the genetic polymorphism IL-6 (rs1800795).

Racial, ethnic, and socioeconomic disparities in the prevalence of cerebral palsy

OBJECTIVE

Racial and ethnic disparities in cerebral palsy have been documented, but the underlying mechanism is poorly understood. We determined whether low birth weight accounts for ethnic disparities in the prevalence of cerebral palsy and whether socioeconomic factors impact cerebral palsy within racial and ethnic groups.

METHODS

In a retrospective cohort of 6.2 million births in California between 1991 and 2001, we compared maternal and infant characteristics among 8397 infants with cerebral palsy who qualified for services from the California Department of Health Services and unaffected infants.

RESULTS

Overall, black infants were 29% more likely to have cerebral palsy than white infants (relative risk: 1.29 [95% confidence interval: 1.19-1.39]). However, black infants who were very low or moderately low birth weight were 21% to 29% less likely to have cerebral palsy than white infants of comparable birth weight. After we adjusted for birth weight, there was no difference in the risk of cerebral palsy between black and white infants. In multivariate analyses, women of all ethnicities who did not receive any prenatal care were twice as likely to have infants with cerebral palsy relative to women with an early onset of prenatal care. Maternal education was associated with cerebral palsy in a dose-response fashion among white and Hispanic women. Hispanic adolescent mothers (aged <18 years) had increased risk of having a child with cerebral palsy.

CONCLUSIONS

The increased risk of cerebral palsy among black infants is primarily related to their higher risk of low birth weight. Understanding how educational attainment and use of prenatal care impact the risk of cerebral palsy may inform new prevention strategies.

Identification of fetal and maternal single nucleotide polymorphisms in candidate genes that predispose to spontaneous preterm labor with intact membranes

OBJECTIVE

The purpose of this study was to determine whether maternal/fetal single nucleotide polymorphisms (SNPs) in candidate genes are associated with spontaneous preterm labor/delivery.

STUDY DESIGN

A genetic association study was conducted in 223 mothers and 179 fetuses (preterm labor with intact membranes who delivered <37 weeks of gestation [preterm birth (PTB)]), and 599 mothers and 628 fetuses (normal pregnancy); 190 candidate genes and 775 SNPs were studied. Single locus/haplotype association analyses were performed; the false discovery rate was used to correct for multiple testing.

RESULTS

The strongest single locus associations with PTB were interleukin-6 receptor 1 (fetus; P=.000148) and tissue inhibitor of metalloproteinase 2 (mother; P=.000197), which remained significant after correction for multiple comparisons. Global haplotype analysis indicated an association between a fetal DNA variant in insulin-like growth factor F2 and maternal alpha 3 type IV collagen isoform 1 (global, P=.004 and .007, respectively).

CONCLUSION

An SNP involved in controlling fetal inflammation (interleukin-6 receptor 1) and DNA variants in maternal genes encoding for proteins involved in extracellular matrix metabolism approximately doubled the risk of PTB.