Role of nitric oxide in chick embryonic organogenesis and dysmorphogenesis

Valproic acid alters nitric oxide status in neurulating mouse embryos

The molecular bases of the teratogenic effects elicited by valproic acid (VPA) are not fully defined. It was previously shown that inhibition of nitric oxide (NO) synthesis is associated with an enhancement of the teratogenic effects of VPA, while amplification of NO signal by sildenafil prompted a dose-dependent reduction of VPA-induced neural tube defects. In this study, for the first time, the effect of VPA on the NO synthesis was evaluated in mouse embryos during early organogenesis. On gestation day 8, ICR-CD1 mice received 600 mg/kg of VPA. Eight and 24 h later embryos were collected and analyzed for NO synthase (NOS) isoform expression, and for molecular mechanisms involved in their modulation. As main finding, in utero embryonic exposure to VPA determined a time-dependent shift of NOS isoforms expression, with a down regulated expression and activity of constitutive NOS (cNOS) and an increased expression and activity of inducible NOS (iNOS). The teratological relevance of this information remains to be established.

Seasonality of fetal trisomy 21--have ambient air pollutants played a role?

OBJECTIVE

To examine the seasonality of fetal trisomy 21 and its relationship with ambient air pollutants.

METHODS

The averaged incidence by month-of-conception of the 113 cases (2002-2009) in our registry was correlated with month of conception and monthly ambient levels of nitrogen oxides (NOx, NO and NO2), sulfur dioxide, carbon monoxide, and ozone as reported by the Hong Kong Environmental Protection Department at the month of, and four-week after, conception.

RESULTS

The incidence was highest in February (3.45/1000 births) and lowest in October (1.28/1000 births), and showed a significant difference (p = 0.003) and positive correlation (p = 0.003) from winter to autumn. It was also correlated with NO (p = 0.017) and inversely with ozone (p = 0.014) at conception.

CONCLUSIONS

Seasonal variation in incidence of fetal trisomy 21 was correlated with ambient levels of nitric oxides and ozone. The role of environmental pollutants on fetal aneuploidy warrants further investigation.

Clinical, genetic and environmental factors associated with congenital vertebral malformations

Congenital vertebral malformations (CVM) pose a significant health problem because they can be associated with spinal deformities, such as congenital scoliosis and kyphosis, in addition to various syndromes and other congenital malformations. Additional information remains to be learned regarding the natural history of congenital scoliosis and related health problems. Although significant progress has been made in understanding the process of somite formation, which gives rise to vertebral bodies, there is a wide gap in our understanding of how genetic factors contribute to CVM development. Maternal diabetes during pregnancy most commonly contributes to the occurrence of CVM, followed by other factors such as hypoxia and anticonvulsant medications. This review highlights several emerging clinical issues related to CVM, including pulmonary and orthopedic outcome in congenital scoliosis. Recent breakthroughs in genetics related to gene and environment interactions associated with CVM development are discussed. The Klippel-Feil syndrome which is associated with cervical segmentation abnormalities is illustrated as an example in which animal models, such as the zebrafish, can be utilized to provide functional evidence of pathogenicity of identified mutations.

Analysis of maternal risk factors associated with congenital vertebral malformations

STUDY DESIGN

A retrospective medical record review of cases with congenital vertebral malformations (CVMs) and controls with normal spine morphology.

OBJECTIVE

To determine the relative contribution of maternal environmental factors (MEFs) during pregnancy to CVM development.

SUMMARY OF BACKGROUND DATA

CVMs represent defects in formation and segmentation of somites occurring with an estimated incidence of between 0.13 and 0.50 per 1000 live births. CVMs may be associated with various phenotypes and represent significant morbidity due to pain and cosmetic disfigurement.

METHODS

A multicenter retrospective medical record review of 229 cases with CVM and 267 controls with normal spine morphology between the ages of 1 and 50 years was performed to obtain the odds ratio (OR) of MEF related to CVM among cases versus controls. An imputation-based analysis was performed in which subjects with no documentation of MEF history were treated as "no maternal exposure." Univariate and multivariate analyses were conducted to calculate the OR.

RESULTS

Of the 229 total cases, 104 cases had single or multiple CVMs without additional congenital malformations (group 1) and 125 cases had single or multiple CVMs and additional congenital malformations (group 2). Nineteen percent of total cases had an identified MEF. The OR for MEF history for group 1 was 6.0 (95% confidence interval, 2.4-15.1; P < 0.001) in the univariate analysis. The OR for MEF history in group 2 was 9.1 (95% confidence interval, 3.8-21.6, P < 0.001) in the univariate analysis. The results were confirmed in the multivariate analysis after adjusting for age, sex, and institution.

CONCLUSIONS

These results support a hypothesis for an association between these MEFs during pregnancy and CVM and have implications for development of prevention strategies. Further prospective studies are needed to quantify association between CVMs and specific MEF.

LEVEL OF EVIDENCE

4.

Developmental abnormalities in chicken embryos exposed to N-nitrosoatrazine

Nitrate and atrazine (ATR) occur in combination in some drinking-water supplies and might react to form N-nitrosoatrazine (NNAT), which is reportedly more toxic than nitrate, nitrite, or ATR. Current evidence from population-based studies indicates that exposure to nitrate, nitrite, and nitrosatable compounds increases the risk of congenital defects and/or rate of embryo lethality. To test the hypothesis that NNAT induces malformations during embryogenesis, chicken embryos were examined for lethality and developmental abnormalities after treating fertilized eggs with 0.06-3.63 μg NNAT. After 5 d of incubation (Hamburger and Hamilton stage 27), 90% of embryos in NNAT-treated eggs were alive, of which 23% were malformed. Malformations included heart and neural-tube defects, caudal regression, gastroschisis, microphthalmia, anophthalmia, and craniofacial hypoplasia. The findings from this investigation suggest further studies are needed to determine the mechanisms underlying NNAT-induced embryotoxicity.

Genetic aspects of congenital and idiopathic scoliosis

Congenital and idiopathic scoliosis represent disabling conditions of the spine. While congenital scoliosis (CS) is caused by morphogenic abnormalities in vertebral development, the cause(s) for idiopathic scoliosis is (are) likely to be varied, representing alterations in skeletal growth, neuromuscular imbalances, disturbances involving communication between the brain and spine, and others. Both conditions are characterized by phenotypic and genetic heterogeneities, which contribute to the difficulties in understanding their genetic basis that investigators face. Despite the differences between these two conditions there is observational and experimental evidence supporting common genetic mechanisms. This paper focuses on the clinical features of both CS and IS and highlights genetic and environmental factors which contribute to their occurrence. It is anticipated that emerging genetic technologies and improvements in phenotypic stratification of both conditions will facilitate improved understanding of the genetic basis for these conditions and enable targeted prevention and treatment strategies.

Gap-Junction Proteins in Retinal Development: New Roles for the “Nexus”

Gap-junction channels, the cytoplasmic proteins that associate with them, and the transcriptional networks that regulate them are increasingly being viewed as critical communications hubs for cell signaling in health and disease. As a result, the term “nexus,” which was the original structural name for these focal intercellular links, is coming back into use with new proteomic and transcriptomic meanings. The retina is better understood than any other part of the vertebrate central nervous system in respect of its developmental patterning, its diverse neuronal types and circuits, and the emergence of its definitive structure-function correlations. Thus, studies of the junctional and nonjunctional nexus roles of gap-junction proteins in coordinating retinal development should throw useful light on cell signaling in other developing nervous tissues.