Methods and systems for determining spatial patterns of biological targets in a sample
The present disclosure provides methods and assay systems for use in spatially encoded biological assays, including assays to determine a spatial pattern of abundance, expression, and/or activity of one or more biological targets across multiple sites in a sample. In particular, the biological targets comprise proteins, and the methods and assay systems do not depend on imaging techniques for the spatial information of the targets. The present disclosure provides methods and assay systems capable of high levels of multiplexing where reagents are provided to a biological sample in order to address tag the sites to which reagents are delivered; instrumentation capable of controlled delivery of reagents; and a decoding scheme providing a readout that is digital in nature.
1. A method of detecting a nucleic acid in a plurality of cells, the method comprising:
(a) delivering the plurality of cells through multiple addressing channels in a microfluidic device, wherein a cell of the plurality of cells is delivered through an addressing channel of the multiple addressing channels, and wherein each addressing channel comprises a probe comprising (i) an address tag having a sequence that uniquely identifies the addressing channel, and (ii) a primer region;
(b) lysing the cell;
(c) hybridizing the nucleic acid from the cell to a portion of the probe in the addressing channel;
(d) extending the probe using the nucleic acid as a template to generate an extended product;
(e) pooling the extended product from each addressing channel; and
(f) determining (i) the address tags for one or more of the addressing channels or a complement thereof, and (ii) all or a portion of the extended product, and using the determined sequences of (i) and (ii) to detecting the nucleic acid in the plurality of cells.
2. The method of claim 1 , further comprising imaging the cell.
3. The method of claim 1 , wherein the multiple addressing channels are substantially parallel to each other.
4. The method of claim 1 , wherein the multiple addressing channels is n addressing channels, wherein n is an integer between 5 and 100.
5. The method of claim 4 , wherein n is an integer between 5 and 20.
6. The method of claim 1 , wherein each of the multiple addressing channels has a width of about 5 μm to about 500 μm.
7. The method of claim 1 , wherein each of the multiple addressing channels has a depth of about 5 μm to about 500 μm.
8. The method of claim 1 , wherein each of the multiple addressing channels has a distance from other multiple addressing channels of about 5 μm to about 2.0 mm.
9. The method of claim 1 , wherein the nucleic acid is an RNA.
10. The method of claim 9 , wherein the RNA is an mRNA.
11. The method of claim 1 , wherein the probe further comprises a variable tag region.
12. The method of claim 1 , wherein the plurality of cells is from a tissue sample.
13. The method of claim 12 , wherein the tissue sample is a freshly isolated tissue sample, a fixed tissue sample, or a frozen tissue sample.
14. The method of claim 1 , wherein the plurality of cells is from cultured cells.
15. The method of claim 1 , further comprising determining (i) the address tag or a complement thereof, and (ii) all or a portion of the extended product by nucleic acid sequencing or high-throughput sequencing.
16. The method of claim 1 , wherein the nucleic acid comprises DNA.
17. The method of claim 16 , wherein the nucleic acid is genomic DNA or mitochondrial DNA.
18. The method of claim 1 , further comprising determining abundance of one or more additional mRNAs in the plurality of cells, wherein the one or more additional mRNAs is an integer between 100 and 30,000.
19. The method of claim 1 , wherein each addressing channel of the multiple addressing channels receives a cell from the plurality of cells.
20. The method of claim 1 , further comprising amplifying the extended product, wherein the amplifying is performed by polymerase chain reaction, wherein the polymerase chain reaction occurs outside the microfluidic device.