Initiation and developmental dynamics of Wfs1 expression in the context of neural differentiation and ER stress in mouse forebrain

Abstract

Wolframin (Wfs1) is a membrane glycoprotein that resides in the endoplasmic reticulum (ER) and regulates cellular Ca(2+) homeostasis. In pancreas Wfs1 attenuates unfolded protein response (UPR) and protects cells from apoptosis. Loss of Wfs1 function results in Wolfram syndrome (OMIM 222300) characterized by early-onset diabetes mellitus, progressive optic atrophy, diabetes insipidus, deafness, and psychiatric disorders. Similarly, Wfs1-/- mice exhibit diabetes and increased basal anxiety. In the adult central nervous system Wfs1 is prominent in central extended amygdala, striatum and hippocampus, brain structures largely involved in behavioral adaptation of the organism. Here, we describe the initiation pattern of Wfs1 expression in mouse forebrain using mRNA in situ hybridization and compare it with Synaptophysin (Syp1), a gene encoding synaptic vesicle protein widely used as neuronal differentiation marker. We show that the expression of Wfs1 starts during late embryonic development in the dorsal striatum and amygdala, then expands broadly at birth, possessing several transitory regions during maturation. Syp1 expression precedes Wfs1 and it is remarkably upregulated during the period of Wfs1 expression initiation and maturation, suggesting relationship between neural activation and Wfs1 expression. Using in situ hybridization and quantitative real-time PCR we show that UPR-related genes (Grp78, Grp94, and Chop) display dynamic expression in the perinatal brain when Wfs1 is initiated and their expression pattern is not altered in the brain lacking functional Wfs1.

Wfs1 is expressed in dopaminoceptive regions of the amniote brain and modulates levels of D1-like receptors

“…As we have previously shown, visual observation of relative gene expression obtained by the enzymatic in situ reaction correlates with the results obtained by using AutoQuantX3 software [22]. Accordingly, we categorized the expression levels as high (+++) when there was a relatively rapidly appearing and strong signal, compared to a moderate (++) stable signal.…”

“…The expression of Wfs1 is specifically strong in the brain regions involved in the emotional control of behavior and the integration of sensory and motor signals [20], [22]. Many of these regions–striatum, cerebral cortex, hippocampus and central extended amygdala–are known to be the targets of dopaminergic pathways [40–41].…”

“…The non-radioactive in situ hybridization was carried out as described in [22]. The mouse Wfs1 riboprobe was the same as in [22].…”

“…The mouse Wfs1 riboprobe was the same as in [22]. cDNA fragment sequences used as templates for Dig-labelled riboprobes for other genes were obtained using the following primers (containing NotI and SalI restrictase sites):…”

“…We and others have previously shown that Wfs1 is enriched in those regions of the rodent brain associated with the control of behaviours and emotions, and with the relay of sensory and motor signals: layer II/III of the cerebral cortex, the CA1 field of the hippocampus, the central extended amygdala, the ventral and dorsal striatum, and various sensory and motor nuclei of the brainstem [19–22]. Functional studies demonstrate that Wfs1 is critical for normal dopamine secretion in the striatum and for dopamine transporter expression in the midbrain [23–24].…”