Effects of Ethanol Exposure In Utero on Cajal–Retzius Cells in the Developing Cortex

Abstract

Background Prenatal exposure to ethanol exerts teratogenic effects on the developing brain. Here, we tested the hypothesis that exposure to ethanol in utero alters the disposition of Cajal–Retzius cells that play a key role in orchestrating proliferation, migration, and laminar integration of cortical neurons in the embryonic cortex. Methods Pregnant Ebf2-EGFP mice, harboring EGFP-fluorescent Cajal–Retzius cells, were subjected to a 2% w/w ethanol consumption regimen starting at neural tube closure and lasting throughout gestation. Genesis of Cajal–Retzius cells was assessed by means of 5-bromo-2-deoxyuridine (BrdU) immunofluorescence at embryonic day 12.5, their counts and distribution were determined between postnatal day (P)0 and P4, patch clamp electrophysiology was performed between P2 and P3 to analyze GABA-mediated synaptic activity, and open-field behavioral testing was conducted in P45-P50 adolescents. Results In Ebf2-EGFP embryos exposed to ethanol in utero, we found increased BrdU labeling and expanded distribution of Cajal–Retzius cells in the cortical hem, pointing to increased genesis and proliferation. Postnatally, we found an increase in Cajal–Retzius cell number in cortical layer I. In addition, they displayed altered patterning of spontaneous GABA-mediated synaptic barrages and enhanced GABA-mediated synaptic activity, suggesting enhanced GABAergic tone. Conclusions These findings, together, underscore that Cajal–Retzius cells contribute to the ethanol-induced aberration of cortical development and abnormal GABAergic neurotransmission at the impactful time when intracortical circuits form.

Chronic Gestational Exposure to Ethanol Leads to Enduring Aberrances in Cortical Form and Function in the Medial Prefrontal Cortex

“…1B, right; Control $\overline{x}=199.7\pm 14.2$ moves; EtOH $\overline{x}=258.7\pm 14.4$ moves; Unpaired t test, P<0.01). In line with our investigation of open field exploratory activity at adolescent ages (Skorput and Yeh, 2015), this hyperactive phenotype confirms that our chronic maternal ethanol consumption regimen is a viable model for investigating the enduring aberrances in cortical form and function associated with FASD.…”

“…However, not examined was whether such a chronic prenatal ethanol exposure-induced aberrant pattern of migration might also be associated with enduring cortical abnormalities later in life. Additionally, our more recent work investigating the teratogenic effects of in utero ethanol exposure on Cajal-Retzius cells during corticogenesis (Skorput and Yeh, 2015) further supports a role for aberrant cortical development in the etiology of FASD. In the present study, we build and expand on these initial studies and ask whether chronic low-level ethanol exposure in utero can lead to FASD-relevant behavioral abnormalities and enduring aberrances in cortical form and function into adulthood.…”

“…Children diagnosed with FASD are hyperactive (Ornoy and Ergaz, 2010; Steinhausen et al, 1993). This hallmark feature can be assessed by comparing the exploratory behavior of adult mice without and with ethanol exposure in utero in an open field arena (Skorput et al, 2015; Skorput and Yeh, 2015). As summarized in Figure 1B, in the prenatal ethanol-exposed adult cohort, we found an increase in the total distance traveled (Fig 1B, left; Control $\overline{x}=2,942\pm 473\text{cm}$, 11 animals from 3 litters; EtOH $\overline{x}=4791\pm 390$, 15 animals from 3 litters; Unpaired t test, P<0.01), amount of time spent in the center of the arena (Fig.…”

“…This study employed the Ebf2-EGFP BAC transgenic mouse line generated by Gene Expression Nervous System Atlas (GENSAT) and obtained from Dr. Portera-Cailliau (UCLA) (Gong et al, 2003; Chowdhury et al, 2010). It should be noted that Ebf2-EGFP BAC mice were used here because the present study was conducted in parallel with another study that focused on investigating Cajal-Retzius cells in the marginal zone of the developing cortex (Skorput and Yeh, 2015). In this mouse line, EGFP selectively labels Cajal-Retzius cells, which have undergone developmental apoptosis and are all but absent in the adult cortex, when the neuroanatomical analyses were performed.…”

Effects of prenatal alcohol exposure (PAE): insights into FASD using mouse models of PAE

“…It was later found that mice receiving the same paradigm exhibited altered patterning of spontaneous GABA-mediated synaptic barrages and increased GABA-mediated synaptic activity, while showing an increase in Cajal-Reizius cell numbers in cortical layer I (Skorput and Yeh 2015). Similar PAE-induced frontal cortex neuron abnormalities have been previously demonstrated in other mouse models implementing a chronic liquid diet for PAE, including the loss of GABAergic neurons in an acute 3rd trimester PAE paradigm (Skorput and Yeh 2015; Smiley et al 2015; Abbott et al 2016), in parallel with the altered neuronal circuitry seen in individuals with FASD (Rema and Ebner 1999; Sowell et al 2008). Importantly, at PN20 PAE, offspring show increased anxiety and impaired gross and fine motor coordination (El Shawa et al 2013).…”