moderate-prenatal-alcohol-exposure-quantification-social-behavior

Moderate Prenatal Alcohol Exposure and Quantification of Social Behavior in Adult Rats

Alterations in social behavior are among the major negative consequences observed in children with Fetal Alcohol Spectrum Disorders (FASDs). Several ...

University of New Mexico

Hu proteins are a family of RNA-binding proteins (RBPs) that are homologs of Drosophila ELAV, a protein required for nervous system development. Three of these proteins (HuB, HuC, and HuD) are primarily expressed in neurons. The fourth member, HuR is ubiquitously expressed in all tissues. At the molecular level, Hu proteins are known to interact with AU-rich instability conferring sequences in the 3' UTR of specific target mRNAs, stabilizing the mRNAs. These proteins are not only the best known mRNA stabilizers but also the earliest markers of the neuronal cell lineage. Among the neuronal Hu proteins, HuD has been shown to accelerate neuronal differentiation and axonal outgrowth in neurons both in culture and in vivo. In addition, HuD and other Hu proteins participate in synaptic plasticity mechanisms in the mature central nervous system and promote regeneration of peripheral nerves. Furthermore, HuD has been implicated in pathological conditions from neurodegenerative disorders such as Parkinson's and Alzheimer's disease to childhood brain tumors. This review will focus on the involvement of HuD in nervous system function and pathology.

Role of HuD in nervous system function and pathology.

The KH-type splicing regulatory protein (KSRP) promotes the decay of AU-rich element (ARE)-containing mRNAs. Although KSRP is expressed in the nervous system, very little is known about its role in neurons. In this study, we examined whether KSRP regulates the stability of the ARE-containing GAP-43 mRNA. We found that KSRP destabilizes this mRNA by binding to its ARE, a process that requires the presence of its fourth KH domain (KH4). Furthermore, KSRP competed with the stabilizing factor HuD for binding to these sequences. We also examined the functional consequences of KSRP overexpression and knockdown on the differentiation of primary hippocampal neurons in culture. Overexpression of full length KSRP or KSRP without its nuclear localization signal hindered axonal outgrowth in these cultures, while overexpression of a mutant protein without the KH4 domain that has less affinity for binding to GAP-43's ARE had no effect. In contrast, depletion of KSRP led to a rise in GAP-43 mRNA levels and a dramatic increase in axonal length, both in KSRP shRNA transfected cells and neurons cultured from Ksrp(+/-) and Ksrp(-/-) embryos. Finally we found that overexpression of GAP-43 rescued the axonal outgrowth deficits seen with KSRP overexpression, but only when cells were transfected with GAP-43 constructs containing 3' UTR sequences targeting the transport of this mRNA to axons. Together, our results suggest that KSRP is an important regulator of mRNA stability and axonal length that works in direct opposition to HuD to regulate the levels of GAP-43 and other ARE-containing neuronal mRNAs.

KSRP modulation of GAP-43 mRNA stability restricts axonal outgrowth in embryonic hippocampal neurons.

Persistent deficits in social behavior are among the major negative consequences associated with exposure to ethanol during prenatal development. Prior work from our laboratory has linked deficits in social behavior following moderate prenatal alcohol exposure (PAE) in the rat to functional alterations in the ventrolateral frontal cortex [21]. In addition to social behaviors, the regions comprising the ventrolateral frontal cortex are critical for diverse processes ranging from orofacial motor movements to flexible alteration of behavior in the face of changing consequences. The broader behavioral implications of altered ventrolateral frontal cortex function following moderate PAE have, however, not been examined. In the present study we evaluated the consequences of moderate PAE on social behavior, tongue protrusion, and flexibility in a variant of the Morris water task that required modification of a well-established spatial response. PAE rats displayed deficits in tongue protrusion, reduced flexibility in the spatial domain, increased wrestling, and decreased investigation, indicating that several behaviors associated with ventrolateral frontal cortex function are impaired following moderate PAE. A linear discriminant analysis revealed that measures of wrestling and tongue protrusion provided the best discrimination of PAE rats from saccharin-exposed control rats. We also evaluated all behaviors in young adult (4-5 months) or older (10-11 months) rats to address the persistence of behavioral deficits in adulthood and possible interactions between early ethanol exposure and advancing age. Behavioral deficits in each domain persisted well into adulthood (10-11 months), however, there was no evidence that aging enhances the effects of moderate PAE within the age ranges that were studied.

Article	Year
Role of HuD in nervous system function and pathology. Frontiers in bioscience (Scholar edition)\| PubMed ID: 23277068	2013
KSRP modulation of GAP-43 mRNA stability restricts axonal outgrowth in embryonic hippocampal neurons. PloS one\| PubMed ID: 24244461	2013
Effects of moderate prenatal ethanol exposure and age on social behavior, spatial response perseveration errors and motor behavior. Behavioural brain research\| PubMed ID: 24769174	2014

Clark W. Bird

Biography

JoVE Journal Publications

Other Publications