Region-specific expression of Dickkopf-like1 in the adult brain Abbreviated title: Dkkl1 in the adult brain

In the adult, the dickkopf family member Dickkopf-like1 (Dkkl1) has been described as a testicular protein involved in the regulation of spermatocyte apoptosis. However, microarray studies additionally suggested that Dkkl1 regulation is involved in various tumors including high grade gliomas. Since investigations of Dkkl1 in the adult central nervous system are lacking, we analyzed Dkkl1 expression in the adult mouse brain and found a region specific expression pattern with a profoundly high cortical expression. Analysis of transgenic mice in which the lacZ gene was inserted into the Dkkl1 locus further pointed to NeuN-positive neurons as the main source of Dkkl1 in the normal adult brain. In Dkkl1−/− mutant mice, gross brain morphology as well as hippocampal and cortical lamination appeared normal. Similarly, neuronal density in cortical layer V was not altered. Thus, Dkkl1 may not be essential for normal brain organization, but could exert import functions during pathological conditions such as tumorigenesis and cancer progression.

► Dickkopf-like1 shows region-specific expression in the adult mouse brain. ► We found significantly high levels of Dickkopf-like1 in the cortex. ► NeuN-positive neurons are the main source of Dickkopf-like1 in the adult cortex. ► Dickkopf-like1 is dispensable for normal brain organization.