Concept profile overlaps were used to score the relationship between all pairs of human genes in the current NCBI Entrez Gene database. Table 1 shows part of the resulting gene-gene relationship matrix, involving hypertension genes. Angiotensin-converting enzyme (ACE) and angiotensinogen (AGT) share 96 specific keyterms, such as 'sodium intake', 'renin-angiotensin-system' and 'blood pressure'; generating a very strong (43.8) link between them. Many of the shared keywords also have relatively high weights. (That is, the frequency is high in abstracts for these genes, compared with all abstracts). In contrast, the link between ACE and arginine vasopressin (AVP) is much weaker, with a score of 0.8, (still above the average for non-zero relationships in the matrix, which is 0.5). There are only two shared keyterms between these genes: 'polydipsia' and 'hypotension'. 'Hypotension' represents a true concept overlap between these two genes, since both are involved in the regulation of blood pressure. 'Polydipsia' is a symptom found in more than one disease. One of these is Autosomal dominant familial neurohypophyseal diabetes insipidus (ADNDI), some times caused by a missense mutation in AVP [62].
