Fto and Postnatal Growth deleted in the neural system. Despite the ubiquitous expression of Fto, its specific deletion in the nervous system results in similar growth retardation phenotypes as the whole body deletion, suggesting that Fto functions in the brain to regulate postnatal growth. Results FTO protein expression in mice We raised antibodies in rabbit against full-length mouse FTO protein and surveyed the expression in various mouse tissues with immunoblotting. Consistent with the previous RT-PCR results [26], the expression of FTO protein was detected in all of the major mouse tissues examined, with the highest level of expression in the brain and the lowest in the skeletal muscle (Figure 1A). Within the brain, FTO is expressed more or less uniformly in different anatomical structures, such as hypothalamus and hippocampus (Figure 1B). Given the association of FTO with human obesity, we wished to determine if the expression of FTO is influenced by food intake. Adult male C57BL/6 mice were fasted for 24 hrs and the FTO expression was examined in energy metabolism-related tissues including white adipose tissue, brown adipose tissue, liver, pancreas, hypothalamus, and skeletal muscle (Figure 1C). However, no obvious changes in the expression of FTO were detected. We also fed male C57BL/6 mice with high fat diet for 17 weeks starting from 6-week-old, and the FTO protein level did not show noticeable changes either (Figure 1D). Thus, if Fto is regulated by food status or type, the regulation is unlikely at the level of protein expression. Previous studies have shown that the Fto mRNA level in the arcuate nucleus (ARC) of the hypothalamus is reduced by fasting in mice [26], and increased by exposure to high fat diet in rats [33]. It is possible these regional changes cannot be detected in the Western blot of whole hypothalamus. Figure 1. FTO protein is ubiquitously expressed in mouse tissues and not affected by nutritional status in mice. (A) Tissues from adult male C57BL/6 mice (except the ovary) were homogenized and immunoblotted. 20 mg total protein was loaded in each lane. (B) Expression of FTO in different regions of the brain. (C) Western blot analysis of FTO in metabolism-related tissues from adult male C57BL/6 mice fed ad libitum or fasted for 24 hrs. (D) Western blot analysis of FTO in tissues from C57BL/6 male mice fed on normal chow or on high fat diet (60 kcal % fat) from 6-week-old for 17 weeks. doi:10.1371/journal.pone.0014005.g001 PLoS ONE | www.plosone.org 2 November 2010 | Volume 5 | Issue 11 | e14005