Mammalian codon optimized nucleotide sequence that encodes a variant opsin polypeptide derived from Natromonas pharaonis (NpHR)
Stimulation of target cells using light, e.g., in vivo or in vitro, is implemented using a variety of methods and devices. One example involves a vector for delivering a light-activated NpHR-based molecule comprising a nucleic acid sequence that codes for light-activated NpHR-based molecule and a promoter. Either a high expression of the molecule manifests a toxicity level that is less than about 75%, or the light-activated NpHR-based proteins are expressed using at least two NpHR-based molecular variants. Each of the variants characterized in being useful for expressing a light-activated NpHR-based molecule that responds to light by producing an inhibitory current to dissuade depolarization of the neuron. Other aspects and embodiments are directed to systems, methods, kits, compositions of matter and molecules for ion pumps or for controlling inhibitory currents in a cell (e.g., in in vivo and in vitro environments).
1. An isolated nucleic acid comprising a mammalian codon optimized nucleotide sequence that encodes a variant opsin polypeptide derived from Natromonas pharaonis (NpHR), wherein the variant NpHR polypeptide comprises a heterologous endoplasmic reticulum (ER) export signal comprising the amino acid sequence set forth in SEQ ID NO: 16, wherein the variant NpHR polypeptide inhibits depolarization of a neuron in response to light of a wavelength that activates the variant NpHR polypeptide, and wherein the variant NpHR polypeptide exhibits reduced toxicity in the neuron compared to toxicity induced by wild-type NpHR.
2. The nucleic acid of claim 1 , wherein the variant NpHR polypeptide comprises a heterologous signal peptide.
3. The nucleic acid of claim 2 , wherein the heterologous signal peptide is a nicotinic acetylcholine receptor signal peptide.
4. The nucleic acid of claim 3 , wherein the heterologous signal peptide comprises the amino acid sequence set forth in SEQ ID NO:13.
5. A recombinant expression vector comprising the nucleic acid of claim 1 .
6. The recombinant expression vector of claim 5 , wherein the nucleotide sequence is operably linked to a neuron-specific promoter.
7. The recombinant expression vector of claim 6 , wherein the neuron-specific promoter is a CaMKIIα promoter.
8. The recombinant expression vector of claim 6 , wherein the neuron-specific promoter is a cholinergic neuron-specific promoter.
9. The recombinant expression vector of claim 5 , wherein the expression vector is a viral expression vector.
10. The recombinant expression vector of claim 9 , wherein the viral expression vector is an adeno-associated viral vector.
11. The nucleic acid of claim 5 , wherein the variant NpHR polypeptide is encoded by nucleotides 1-873 of SEQ ID NO:1.
12. The recombinant expression vector of claim 9 , wherein the viral expression vector is a lentivirus vector.