Co-localization of Sorting Nexin 2 and androgen receptor in the song system of juvenile zebra finches

Abstract

Mechanisms regulating sexual differentiation of the zebra finch song system appear to include both genetic and hormonal factors. Sorting Nexin 2 (SNX2), which is involved in trafficking proteins between cellular membranes, and androgen receptor (AR) mRNA are both increased in song control nuclei of juvenile males compared to females. Here, in situ hybridization for SNX2 and immunohistochemistry for AR were used to evaluate these sexual dimorphisms in more detail. Estimates of the total number of HVC cells expressing SNX2 and AR, individually as well as together, were greater in 25-day-old males compared to females. The densities of these types of cells were generally also increased in males compared to females in HVC and Area X (or the equivalent portion of the medial striatum in females). On average, more than half of the AR+ cells co-expressed SNX2 in both brain regions. The potential, therefore, exists for both AR and SNX2 to be involved in masculinization of these two brain regions. One possibility is that they, either separately or in conjunction, enhance the action of trophic factors within the brain.

The effects of estradiol on 17β-hydroxysteroid dehydrogenase type IV and androgen receptor expression in the developing zebra finch song system

“…Males had a significantly higher degree of co-localization (AR cells expressing HSD17B4) in HVC in comparison to females. These results mirror those found with sorting nexin 2 and ribosomal proteins L17 and L37 (Tang & Wade, 2010; Wu et al, 2010), and collectively point to the possibility that the co-localization of a variety of Z-chromosome genes and AR may be important for the masculinization of the song system. However, E2 treatments had no effect on the extent of the co-localization in the present study.…”

“…This is surprising, since earlier work documented a sex difference in AR protein expression in Area X at this same age (Wu, et al, 2010). However, mismatches between mRNA and protein expression do occur(Chen et al, 2002; Greenbaum et al, 2003), and Wu and colleagues (2010) quantified the total number of cells expressing AR-ir rather than the number within a specified area as we did. Another study (Kim, et al, 2004) measured mRNA and also found a sex difference.…”

“…Studies have identified specific genes that are both sex-linked and expressed at increased levels in the male than the female song system (Chen et al, 2005; Duncan & Carruth, 2007; Tang et al, 2007; Tang & Wade, 2006; Tomaszycki et al, 2009). Recent research suggests that some of these genes may interact with AR to facilitate masculinization (Tang & Wade, 2010; Wu, et al, 2010). …”

Status-appropriate singing behavior, testosterone and androgen receptor immunolabeling in male European starlings (Sturnus vulgaris)

“…Western blot was used to test specificity of the antibody N-20 (sc-816, Santa Cruz Biotech) a polyclonal antibody raised against a peptide mapping at the N-terminus of AR of human origin that has been used in zebra finches, quail and chickens (Kharwar and Haldar, 2011; Shaw and Kennedy, 2002; Tang and Wade, 2010, 2011; Wu et al, 2010). Micropunched tissue from starling and mouse was homogenized with ice-cold lysis buffer (1.0 mL/100 mg of tissue) in pre-chilled centrifuge tubes.…”

Sex- and age-related differences in ribosomal proteins L17 and L37, as well as androgen receptor protein, in the song control system of zebra finches

“…Omission of the primary AR antibody also eliminated labeling in zebra finch brain (Wu et al, 2010). Additional tests were conducted for this set of studies.…”