Introduction to gimVI

Imputing missing genes in spatial data from sequencing data with gimVI

!pip install --quiet scvi-colab
from scvi_colab import install

install()

import anndata
import matplotlib.pyplot as plt
import numpy as np
import scanpy
import scvi
from scipy.stats import spearmanr
from scvi.data import cortex, smfish
from scvi.external import GIMVI

scvi.settings.seed = 0
print("Last run with scvi-tools version:", scvi.__version__)

train_size = 0.8

%config InlineBackend.print_figure_kwargs={'facecolor' : "w"}
%config InlineBackend.figure_format='retina'

spatial_data = smfish()
seq_data = cortex()

INFO     File                                                                                
         /data/yosef2/users/jhong/scvi-tutorials/data/osmFISH_SScortex_mouse_all_cell.loom   
         already downloaded                                                                  
INFO     Loading smFISH dataset                                                              
INFO     File /data/yosef2/users/jhong/scvi-tutorials/data/expression.bin already downloaded 
INFO     Loading Cortex data from /data/yosef2/users/jhong/scvi-tutorials/data/expression.bin
INFO     Finished loading Cortex data                                                        

Preparing the data

In this section, we hold out some of the genes in the spatial dataset in order to test the imputation results

# only use genes in both datasets
seq_data = seq_data[:, spatial_data.var_names].copy()

seq_gene_names = seq_data.var_names
n_genes = seq_data.n_vars
n_train_genes = int(n_genes * train_size)

# randomly select training_genes
rand_train_gene_idx = np.random.choice(range(n_genes), n_train_genes, replace=False)
rand_test_gene_idx = sorted(set(range(n_genes)) - set(rand_train_gene_idx))
rand_train_genes = seq_gene_names[rand_train_gene_idx]
rand_test_genes = seq_gene_names[rand_test_gene_idx]

# spatial_data_partial has a subset of the genes to train on
spatial_data_partial = spatial_data[:, rand_train_genes].copy()

# remove cells with no counts
scanpy.pp.filter_cells(spatial_data_partial, min_counts=1)
scanpy.pp.filter_cells(seq_data, min_counts=1)

# setup_anndata for spatial and sequencing data
GIMVI.setup_anndata(spatial_data_partial, labels_key="labels", batch_key="batch")
GIMVI.setup_anndata(seq_data, labels_key="labels")

# spatial_data should use the same cells as our training data
# cells may have been removed by scanpy.pp.filter_cells()
spatial_data = spatial_data[spatial_data_partial.obs_names]

Creating the model and training

# create our model
model = GIMVI(seq_data, spatial_data_partial)

# train for 200 epochs
model.train(200)

Epoch 1/200:   0%|          | 0/200 [00:00<?, ?it/s]Epoch 200/200: 100%|██████████| 200/200 [04:08<00:00,  1.24s/it, loss=24.5, v_num=1]

Analyzing the results

Getting the latent representations and plotting UMAPs

# get the latent representations for the sequencing and spatial data
latent_seq, latent_spatial = model.get_latent_representation()

# concatenate to one latent representation
latent_representation = np.concatenate([latent_seq, latent_spatial])
latent_adata = anndata.AnnData(latent_representation)

# labels which cells were from the sequencing dataset and which were from the spatial dataset
latent_labels = (["seq"] * latent_seq.shape[0]) + (
    ["spatial"] * latent_spatial.shape[0]
)
latent_adata.obs["labels"] = latent_labels

# compute umap
scanpy.pp.neighbors(latent_adata, use_rep="X")
scanpy.tl.umap(latent_adata)

# save umap representations to original seq and spatial_datasets
seq_data.obsm["X_umap"] = latent_adata.obsm["X_umap"][: seq_data.shape[0]]
spatial_data.obsm["X_umap"] = latent_adata.obsm["X_umap"][seq_data.shape[0] :]

# umap of the combined latent space
scanpy.pl.umap(latent_adata, color="labels", show=True)

# umap of sequencing dataset
scanpy.pl.umap(seq_data, color="cell_type")

# umap of spatial dataset
scanpy.pl.umap(spatial_data, color="str_labels")

Getting Imputation Score

imputation_score() returns the median spearman r correlation over all the cells

# utility function for scoring the imputation


def imputation_score(model, data_spatial, gene_ids_test, normalized=True):
    _, fish_imputation = model.get_imputed_values(normalized=normalized)
    original, imputed = (
        data_spatial.X[:, gene_ids_test],
        fish_imputation[:, gene_ids_test],
    )

    if normalized:
        original /= data_spatial.X.sum(axis=1).reshape(-1, 1)

    spearman_gene = []
    for g in range(imputed.shape[1]):
        if np.all(imputed[:, g] == 0):
            correlation = 0
        else:
            correlation = spearmanr(original[:, g], imputed[:, g])[0]
        spearman_gene.append(correlation)
    return np.median(np.array(spearman_gene))


imputation_score(model, spatial_data, rand_test_gene_idx, True)

0.18909629468647293

Plot imputation for Lamp5, which should have been hidden in the training

# utility function for plotting spatial genes


def plot_gene_spatial(model, data_spatial, gene):
    data_seq = model.adatas[0]
    data_fish = data_spatial

    fig, (ax_gt, ax) = plt.subplots(1, 2)

    if type(gene) == str:
        gene_id = list(data_seq.gene_names).index(gene)
    else:
        gene_id = gene

    x_coord = data_fish.obs["x_coord"]
    y_coord = data_fish.obs["y_coord"]

    def order_by_strenght(x, y, z):
        ind = np.argsort(z)
        return x[ind], y[ind], z[ind]

    s = 20

    def transform(data):
        return np.log(1 + 100 * data)

    # Plot groundtruth
    x, y, z = order_by_strenght(
        x_coord, y_coord, data_fish.X[:, gene_id] / (data_fish.X.sum(axis=1) + 1)
    )
    ax_gt.scatter(x, y, c=transform(z), s=s, edgecolors="none", marker="s", cmap="Reds")
    ax_gt.set_title("Groundtruth")
    ax_gt.axis("off")

    _, imputed = model.get_imputed_values(normalized=True)
    x, y, z = order_by_strenght(x_coord, y_coord, imputed[:, gene_id])
    ax.scatter(x, y, c=transform(z), s=s, edgecolors="none", marker="s", cmap="Reds")
    ax.set_title("Imputed")
    ax.axis("off")
    plt.tight_layout()
    plt.show()


assert "Lamp5" in rand_test_genes
plot_gene_spatial(model, spatial_data, 9)