METHODS OF MAINTAINING, EXPANDING, AND DIFFRENTIATING NEURONAL SUBTYPE SPECIFIC PROGENITORS

1 . A method for maintaining a population of neuronal subtype-specific progenitors, the method comprising culturing neuronal subtype-specific progenitors in a culture medium comprising a Wnt signaling pathway agonist, an inhibitor of the bone morphogenetic protein (BMP) signaling pathway, an inhibitor of the transforming growth factor beta (TGFIβ) signaling pathway, and a Notch signaling pathway agonist, whereby expression of a neuronal subtype-specific progenitor gene expression profile is maintained in the neuronal subtype-specific progenitors.

2 . The method of claim 1 , wherein the neuronal subtype-specific progenitors have a gene expression profile comprising expression of at least one of SOX1, SOX2, NESTIN, N-Cadherin, and Ki67.

3 . The method of claim 2 , wherein the neuronal subtype-specific progenitors are spinal neural progenitors having a gene expression profile further comprising expression of at least one of HOXA5 and HOXB8, and substantially no expression of midbrain, hindbrain, or forebrain markers.

4 . The method of claim 3 , wherein the spinal neural progenitors are OLIG2 + spinal motor neuron progenitors.

5 . The method of claim 2 , wherein the neuronal subtype-specific progenitors are hindbrain neural progenitors having a gene expression profile further comprising expression of at least one of GBX2, KROX20, HOXA1-4, and HOXB1-4, and substantially no expression of forebrain, spinal cord, or midbrain markers.

6 . The method of claim 5 , wherein the hindbrain neural progenitors are NKX2.2 + hindbrain serotonergic neural progenitors.

7 . The method of claim 2 , wherein the neuronal subtype-specific progenitors are midbrain neural progenitors having a gene expression profile further comprising expression of at least one of EN1 and EN2, and substantially no expression of forebrain, spinal cord, or hindbrain markers.

8 . The method of claim 7 , wherein the midbrain neural progenitors are LMX1A + midbrain dopaminergic neuron progenitors.

9 . The method of claim 2 , wherein the neuronal subtype-specific progenitors are forebrain neural progenitors having a gene expression profile further comprising expression of at least one of FOXG1 and OTX2, and substantially no expression of midbrain, spinal cord, or hindbrain markers.

10 . The method of claim 9 , wherein the forebrain neural progenitors are NKX-2.1 + forebrain GABAergic neuron progenitors.

11 . The method of claim 1 , wherein the Wnt signaling pathway agonist is a GSK3 inhibitor selected from the group consisting of CHIR99021 and 6-bromo-iridium-3′-oxime.

12 . The method of claim 1 , wherein the BMP signaling pathway inhibitor is selected from the group consisting of DMH-1, Dorsomorphin, and LDN-193189.

13 . The method of claim 1 , wherein the Notch signaling pathway agonist is a histone deacetylase (HDAC) inhibitor selected from the group consisting of valproic acid (VPA), suberoyl bis-hydroxamic acid (SBHA), and sodium butyrate.

14 . The method of claim 1 , wherein the TGFIβ signaling pathway inhibitor is selected from the group consisting of SB431542, SB505124, and A83-01.

15 . The method of claim 1 , wherein the culture medium comprises CHIR99021, DMH-1, SB431542, and VPA.

16 . The method of claim 15 , wherein the culture medium comprises between about 1 μM-3 μM CHIR99021; about 1 μM-5 μM DMH-1; about 1 μM-5 μM SB431542; and about 0.2-μM-2 μM VPA.

17 . The method of claim 4 , wherein the neuronal subtype specific progenitors are OLIG2 + spinal motor neuron progenitors, and wherein the culture medium comprises CHIR99021, DMH-1, SB431542, VPA, a SHH pathway agonist, and a RA pathway agonist.

18 . The method of claim 17 , wherein the SHH pathway agonist is selected from the group consisting of purmorphamine and SAG (Smoothened Agonist).

19 . The method of claim 17 , wherein the RA pathway agonist is retinoic acid.

20 . The method of claim 17 , wherein the culture medium comprises between about 1 μM to 3 μM CHIR99021; about 1 μM to 5 μM DMH-1; about 1 μM to 5 μM SB431542; about 0.2 μM-2 μM VPA; and about 0.1 μM to 1 μM purmorphamine; about 0.01 μM to 1 μM RA.

21 . The method of claim 17 , wherein the OLIG2 + spinal motor neuron progenitors are maintained in a culture substantially free of MNX1 + post-mitotic motor neurons for at least 5 weeks.

22 . The method of claim 17 , wherein the OLIG2 + spinal motor neuron progenitors are maintained in a culture substantially free of MNX1 + post-mitotic motor neurons for at least 10 weeks.

23 . The method of claim 6 , wherein the neuronal subtype specific progenitors are NKX2.2 + hindbrain serotonergic neural progenitors, and wherein the culture medium comprises CHIR99021, DMH-1, SB431542, VPA, and purmorphamine.

24 . The method of claim 23 , wherein the culture medium comprises about 1 μM to 3 μM CHIR99021; about 1 μM to 5 μM DMH-1; about 1 μM to 5 μM SB431542; about 0.2 μM-2 μM VPA; and about 0.1 μM to 1 μM purmorphamine

25 . The method of claim 23 , wherein the NKX2.2 + hindbrain serotonergic neural progenitors are maintained substantially free from differentiation for at least 5 weeks.

26 . The method of claim 23 , wherein the NKX2.2 + hindbrain serotonergic neural progenitors are maintained substantially free from differentiation for at least 10 weeks.

27 . The method of claim 1 , wherein the neuronal subtype specific progenitors are obtained from pluripotent stem cells.

28 . The method of claim 27 , wherein the pluripotent stem cells are human pluripotent stem cells.

29 . The method of claim 28 , wherein the human pluripotent stem cells are human embryonic stem cells.

30 . The method of claim 28 , wherein the human pluripotent stem cells are human induced pluripotent stem cells.

31 . The method of claim 1 , wherein the neuronal subtype specific progenitors are obtained from a human embryo.