Table 2.

Biological features associated with the direct reprogramming process.

Stages (wpi)	Major biological features	References
1	High expression of the reprogramming factors and reporter; chromatin remodeling; changes of global gene expression	This study and Smith et al. (2016)
2	Morphological changes with extensive neurite outgrowths; expression of neuronal markers such as TUBB3 and nuclear HB9 in diMNs	This study and Liu et al. (2016)
3	Expression of genes essential for neuronal function: voltage-gated channels, neurotransmitters, transporters, pre- and post-synaptic proteins, etc.; high levels of mRNAs in the nucleus	This study and Mertens et al. (2015)
4	Complex multipolar morphology; robust expression of markers for mature neurons including MAP2 and CHAT; high nuclear mRNA levels	This study and Liu et al. (2016)
6	Typical neuronal morphology; high levels of markers for mature neurons such as CHAT, VAChT, and synaptic proteins; reduced nuclear mRNA levels	This study and Liu et al. (2016)
8	Fully functional neurons with synaptogenesis and mature electrophysiology; formation of neuromuscular junctions between diMNs and myotubes	Liu et al. (2016)

TUBB3, tubulin beta 3 class III; MAP2, microtubule-associated protein 2; CHAT, choline acetyltransferase; VAChT, vesicular acetylcholine transporter.