Birthdays of retinal amacrine cell subtypes are systematically related to their molecular identity and soma position

Abstract

The mammalian retina contains six major cell types, several of which are divided into multiple molecularly and morphologically distinct subtypes. To understand how subtype diversity arises during development, we focused on amacrine interneurons in the mouse retina; ~30 amacrine subtypes have been identified in mammals. We used antibody markers to identify the two main amacrine subsets – GABAergic and glycinergic – and further subdivided these groups into smaller subsets based on expression of neurotransmitter and transcription factor markers. We then used bromodeoxyuridine (BrdU) labeling to ask whether amacrine subsets are born (become postmitotic) at different times, as is the case for lamina-specified subsets of cortical projection neurons. We found that GABAergic amacrines are generated on average 2–3 days before glycinergic amacrines. Moreover, subsets of GABAergic amacrines are born at distinct times. We also found a strong correlation between amacrine cell birthday and soma position in the mature retina, another point of similarity with cortical projection neurons. This relationship raised the possibility that amacrine subtype identity is determined by signals that uncommitted cells receive after they migrate to their destinations. However, cells labeled with BrdU in vivo, then dissociated and allowed to develop in vitro, acquired the amacrine subtype-specific markers appropriate for their birthdays, supporting the idea that they become specified near the time and place of their birth. Together, our results suggest that the birthdays of amacrine cells independently specify their destinations and subtype identities.

Prolonged Expression of Puma in Cholinergic Amacrine Cells During the Development of Rat Retina

“…The labeling pattern that we observed was indistinguishable from that of the previous report (Voinescu et al 2009). …”

Lgr5 + amacrine cells possess regenerative potential in the retina of adult mice

“…Retinogenesis in mice begins during embryogenesis at embryonic day 10 (E10) to E11 when the optic vesicle invaginates to form the optic cup and is completed by postnatal day 15 (P15) (Pei & Rhodin, 1970). Amacrine cells are generated over a broad temporal window, starting shortly after the optic cup is formed and lasting until P5 to P6 (Voinescu et al ., 2009). The Lgr5-EGFP signal was detected shortly after optic vesicle invagination on E10.5 in both layers of the optic cup and surrounding mesenchymal cells.…”

Development of Dendritic Form and Function

“…A similar principle operates in the vertebrate retina, where subtypes of RGCs and amacrine cells-identified by their physiological light responses, neurotransmitter phenotypes, or gene expression profiles-have stereotyped dendritic projections to IPL sublayers (Figure 4a) (Famiglietti & Kolb 1976, Siegert et al 2009, Wässle 2004. RGC and amacrine subtype fate choices, including laminar-targeting decisions, are correlated with and likely specified by birthdate (Cherry et al 2009, De la Huerta et al 2012, Osterhout et al 2014, Voinescu et al 2009). A few transcription factors controlling laminar choice have been identified, but none of these alter IPL stratification without changing other aspects of cell fate, such as neurotransmitter type (Cherry et al 2011, Kay et al 2011.…”