add gtf parser requirements to README

README.md

@@ -168,6 +168,14 @@ R2Dtool is designed to work with tab-delimited, plain text BED-like files (optio
 
 The GTF annotation provided must contain identical gene structures used to generate the transcriptome, including identical transcript names in the FASTA header. One option is to use genomes, transcriptomes and gene structures from the same genome release. Another option is for users to generate their own transcriptome using a genome and gene structure file, e.g. using gffread.  
 
+# Gene annotation requirements 
+
+R2Dtool is designed to work with GTF version 2 annotations
+
+- Compatible feature types (col3) include 'transcript'/'mRNA', 'exon', 'CDS', 'five_prime_utr'/'5UTR' and 'three_prime_utr'/'3UTR' 
+- 'exon', 'transcript', and 'UTR' feature types are __required__ for liftover and annotation 
+- Column 9 should contain 'transcript_id', 'gene_id', 'gene_name', and some variety of biotype attribute (e.g. 'transcript_biotype', 'transcript_type', 'gene_type', or 'gene_biotype')
+
 # Utilities
 
 ### Convert CHEUI model II output to a BED-like input