Biology of Genes and Proteins

It is suggested that in Drosophila, the DSCAM gene may produce more than 38,000 mRNAs encoding different proteins. Among an array of mRNA, not all mRNAs are translatable for a variety of reasons, including the presence of an early stop codon. Alternate splicing may be tissue specific and 

Intron retention results in the production of mRNAs and their encoded proteins of different lengths. Intron retention is commonly found in plants and lower multicellular organisms. 

Splicing is facilitated by splicosomes that consist of more than 100 proteins and five small nuclear (sn) RNAs (snRNAs). Certain regulatory proteins called splicing regulator (SR) proteins bind to a particular nucleotide sequence in the exon called the exon splicing enhancer (ESE) and recruit splicosomes. The exon may contain an exon splicing suppressor (ESS) sequence, which prevents the splicosome from splicing. 

Defective splicing may cause diseases in humans. More than 15% of mutations that cause diseases in humans result in defective splicing. Defective splicing may result in mutations that alter the splice site or the components of splicesosomes, or it may change factors that control splicing. 

Many human diseases including cancer may involve mutations that cause defective splicing (Faustino and Cooper 2003). Some genes in which a mutation is known to cause defective splicing and human diseases include BRCA1 BRCA2, HGH, cystic fibrosis spinal muscular atrophy (SMA), myotonic dystrophy (MD), Wilms tumor suppressor associated with Frasier syndrome (WT1), and many more. 

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