Extended Data figure 7: Temporal transcriptions factors are inherited in neurons and regulate neuronal diversity.

(a) UMAP plots showing the expression of all temporal transcription factors in the developing Drosophila optic lobe. (a) Hth maintains its expression in some of their neuronal progeny, such as Mi1, Pm1, and Pm2. (a’) On the other hand, ey, D, erm and Scro not only maintain their expression in some neuronal progeny, but they are also activated independently in neuronal types that come from different temporal windows. Hence, most of them are expressed in both early- and late-born neuronal types (see also Supplementary Table 1). (a’’) Slp1, opa, BarH1, Oaz, and tll do not maintain their transcription in neurons. However, using their expression in GMCs at the root of neuronal branches, we can predict neuronal types that come from these temporal windows (such Tm1, Tm2, and Tm4 for Opa). (a’’’) Finally, hbn is not maintained in neuronal progeny of the Hbn+ neuroblasts, but it is activated independently in later-born neurons (such as T1). Neuronal types that come from the relevant temporal windows are indicated.

(b) Expression of temporal transcription factors in neuronal progeny shows that the tTFs are expressed in the newly born progeny of their respective neuroblast temporal window. Time is depicted by the arrow; neurons born from young neuroblasts are on the top of the Figure. Opa-positive neurons are born from young neuroblasts (red), followed by Erm neurons (green). Then, neurons expressing Hbn and Opa can be detected. (red-white). Finally, Scro-positive (blue) and Scro and BarH1-positive neurons (blue-white) are born from older neuroblasts. Single-channel images can be seen in the right panels.

(c) Hbn is involved in the generation of neuronal diversity by regulating the expression of downstream transcription factors. In Hbn-mutant MARCM clones (green) neurons expressing Toy, Otd (c) and Tj (c’) are not found.

(d) Opa is also involved in the generation of neuronal diversity by regulating the expression of the downstream transcription factor TfAP-2 in some neurons. Opa-mutant MARCM clones (green) have fewer TfAP-2 positive cells (magenta) compared to the adjacent wild-type tissue.

Scale bars: 10 μm