Dillon Byerley

Background: Fetal Alcohol Spectrum Disorders (FASD) encompass a wide variety of clinical manifestations, all which are a result of varying levels of fetal alcohol exposure in utero. Some of these manifestations include disruption of neurological development, facial abnormalities, brain abnormalities, skeletal abnormalities and even some behavioral abnormalities such as aggression¹. FASD affects millions of people across the globe, with estimates of 25 million people worldwide being affected¹. There are myriad hypotheses for the primary mechanisms contributing to pathology in FASD. For the facial deficits often observed in FASD, the impact of ethanol exposure on cranial neural crest cell (NCC) development, migration, and survival has a tremendous impact². Some mechanisms by which ethanol may impair NCC migration include its inhibition of epithelial-mesenchymal transition (EMT)³, chemotactic impairment, and disruption of homocysteine equilibrium^2,3. Furthermore, ethanol seems to impact NCC differentiation by disrupting microRNA function³ and reducing autophagy in NCC’s. Finally, ethanol negatively impacts NCC survival by promoting apoptosis^2,3.

Objective: The goal of this literature review was to gain a greater understanding of ethanol’s impact on neural crest development, and how microRNAs can potentially be manipulated to alleviate some of these ethanol-induced defects.

Search Methods: The papers in this review were found on the PubMed database using the following keywords and/or MeSH terms: “ethanol,” “neural crest,” “microRNAs,” and “fetal alcohol spectrum disorders.”

Results: Overall, the papers included in this literature review all illustrated how manipulation of various microRNAs in a cell culture and/or zebrafish embryo can reverse many of the ethanol-induced defects in neural crest cell development. For example, inhibition of microRNA-34a in an ethanol exposed neural crest cell culture was shown to largely restore epithelial-mesenchymal transition by reducing expression of E-cadherin (EMT inhibitor) and increasing expression of Vimentin (EMT activator).³ Additionally, inhibition of microRNA-34a in an ethanol exposed NCC culture also increased expression of Atg9a (a pro-autophagy protein), largely restoring autophagy in these cells.⁴ Furthermore, transfection of microRNA-135a decreased expression of Siah1 (a pro-apoptotic protein) in both ethanol exposed zebrafish embryos and NCC culture, indicating that this microRNA can prevent ethanol-induced NCC apoptosis.⁵ Another study showed that addition of a microRNA-126 inhibitor to an NCC and placode cell (PC) co-culture increases the expression of SDF1 (a chemotactic agent), thus improving the interaction between NCC’s and PC’s and improving NCC migration overall.⁶ Finally, a clinical study, which compared circulating microRNA levels in ethanol-exposed infants to a control group, indicated that microRNA levels in infants have the potential to be used as a diagnostic tool to measure prenatal ethanol exposure and to predict the extent of future disability.⁷ This may allow for earlier intervention in patients with FASD.

Conclusion: In conclusion, these studies demonstrated that alteration of various microRNAs can mitigate the effects of ethanol exposure on NCC development in vitro and in vivo, allowing for restoration of craniofacial development and prevention of ethanol-induced defects. Additional human studies are needed to gain further understanding of microRNAs’ potential in FASD diagnosis and treatment.

Works Cited:

1. Popova S, Charness ME, Burd L, Crawford A, Hoyme HE, Mukherjee RAS, Riley EP, Elliott EJ. Fetal alcohol spectrum disorders. Nat Rev Dis Primers. 2023 Feb 23;9(1):11. doi: 10.1038/s41572-023-00420-x. PMID: 36823161.
2. Chen SY, Kannan M. Neural crest cells and fetal alcohol spectrum disorders: Mechanisms and potential targets for prevention. Pharmacol Res. 2023 Aug;194:106855. doi: 10.1016/j.phrs.2023.106855. Epub 2023 Jul 17. PMID: 37460002; PMCID: PMC10528842.
3. Fan H, Li Y, Yuan F, Lu L, Liu J, Feng W, Zhang HG, Chen SY. Up-regulation of microRNA-34a mediates ethanol-induced impairment of neural crest cell migration in vitro and in zebrafish embryos through modulating epithelial-mesenchymal transition by targeting Snail1. Toxicol Lett. 2022 Apr 1;358:17-26. doi: 10.1016/j.toxlet.2022.01.004. Epub 2022 Jan 14. PMID: 35038560; PMCID: PMC9058190.
4. Fan H, Yuan F, Yun Y, Wu T, Lu L, Liu J, Feng W, Chen SY. MicroRNA-34a mediates ethanol-induced impairment of neural differentiation of neural crest cells by targeting autophagy-related gene 9a. Exp Neurol. 2019 Oct;320:112981. doi: 10.1016/j.expneurol.2019.112981. Epub 2019 Jun 24. PMID: 31247197; PMCID: PMC6708457
5. Yuan F, Yun Y, Fan H, Li Y, Lu L, Liu J, Feng W, Chen SY. MicroRNA-135a Protects Against Ethanol-Induced Apoptosis in Neural Crest Cells and Craniofacial Defects in Zebrafish by Modulating the Siah1/p38/p53 Pathway. Front Cell Dev Biol. 2020 Oct 2;8:583959. doi: 10.3389/fcell.2020.583959. PMID: 33134300; PMCID: PMC7561719.
6. Li Y, Cai T, Liu H, Liu J, Chen SY, Fan H. Exosome-shuttled miR-126 mediates ethanol-induced disruption of neural crest cell-placode cell interaction by targeting SDF1. Toxicol Sci. 2023 Sep 28;195(2):184-201. doi: 10.1093/toxsci/kfad068. PMID: 37490477; PMCID: PMC10801442.
7. Mahnke AH, Sideridis GD, Salem NA, Tseng AM, Carter RC, Dodge NC, Rathod AB, Molteno CD, Meintjes EM, Jacobson SW, Miranda RC, Jacobson JL. Infant circulating MicroRNAs as biomarkers of effect in fetal alcohol spectrum disorders. Sci Rep. 2021 Jan 14;11(1):1429. doi:10.1038/s41598-020-80734-y. PMID: 33446819; PMCID: PMC7809131.