The physics department at Texas State University is developing a Learning Assistant (LA) program with reform-based instructional changes in our introductory course sequences. We are interested in how participation in the LA program influences LAs' identity both as physics students and as physics teachers; in particular, how being part of the LA community changes participants' self-concepts and their day-to-day practice. We analyze written artifacts from program applications, reflections, and evaluations; our analysis of self-concepts is informed by the identity framework developed by Hazari and colleagues [1,2] and our analysis of practice is informed by Lave and Wenger's theory of Communities of Practice [3,4]. Preliminary experience suggests that engagement in the collaborative physics education community elements of the LA program blurs the distinction between learner and teacher practice and increases LAs' engagement in negotiation of meaning in both contexts.