grp_id: ID of phenotype group (gene_id)
grp_chr: chromosome of phenotype group (gene)
grp_start, grp_end: start and end positions of phenotype group (gene)
grp_strand: strand of phenotype group (gene)
intron: intron identifier formatted as per leafcutter (chromosome:start:end:clu_clusterid_clusterstrand_stimulants_timepoint)
n_intron_in_grp: number of phenotypes (introns) in the phenotype group (gene)
n_var_in_cis: number of variants in the cis window of the phenotype group (1mbp of gene start position)
dist_intron_var: distance between variant and phenotype (intron)
var_id: variant rsid (if available. otherwise variant_chr:position)
var_chr: variant chromosome
variant_start, variant_end: variant start and end positions
pvalue_nominal: nominal p-value of the association between the most significant variant and the phenotype group (gene).
r_squared: R^2 of the linear regression between phenotype (intron) and variant 
slope: beta (slope) of the linear regression between phenotype (intron) and variant
slope_se: standard error of the beta (slope).
best_hit: whether variant is the variant with the smallest nominal P-value per phenotype group (gene)
N_cond: number of RNA-seq samples in condition
macromap_MAF: minor allele frequency (MAF) of variant in macromap