Pseudogenes and their formation - Human Gene Evolution - page 267

Table 6.1 (continued)

Pseudogene Complete/partial Comments Reference

Prostaglandin EP4 Complete Unclear if linked to Foord et al . (1996)

receptor (2) PTGER4 gene (5p13)

Adrenoleukodystrophy Partial (exons 7-10) Unclear if linked to Braun et al . (1996)

ALD gene at Xq28.

-Globin Complete Linked to HBB Chang and Slightom

(1984) gene (11p15)

Aldehyde Complete Transcribed Hsu and Chang (1996);

dehydrogenase Hsu et al . (1997)

( ALDH8 )
Iduronate-2-sulfatase Partial (exons 2 and 3, Linked to IDS gene (Xq28). Timms et al . (1995);

introns 2 and 7) Not transcribed. Rathmann et al . (1995)

Numbers in brackets denote numbers of pseudogenes in cases where more than one has been found.

Myrs ago (Horiuchi et al ., 1993). This pseudogene contains three inactivating
mutations: an 8 bp deletion in exon 3, the insertion of a T in exon 7 and a non-
sense mutation in exon 8 (Kawaguchi et al ., 1992). The 8 bp deletion is present in
both humans and chimpanzees whereas the other two mutations are human-spe-
cific (Kawaguchi et al ., 1992) consistent with the 8 bp deletion being the original
inactivating mutation in the human-chimpanzee lineage. In gorilla and orang-
utan, the extra Cyp21 gene copies are inactivated by various other mutations
(Kawaguchi et al., 1992).
From inspection of Table 6.1 , it is apparent that such pseudogenes are essen-
tially of two types: either complete copies of the source gene or partial copies of
that gene. Complete copies tend to be linked to the source gene (examples given
in Figure 6.2 ) whereas partial copies are often (although not always) unlinked to

~65 kb

-Globin
gene cluster
11p15.5

LCR

HBE1 HBG2 HBG1 HBBP1 HBD HBB

~75 kb

α -Globin
gene cluster
16p13.3

LCR

HBZ HBZP

HBAP2

HBAP1 HBA1 HBQ1

HBA2

~50 kb

LCR

Growth hormone
gene cluster
17q22-q24

GH1 CSHP1 CSH1 GH2 CSH2

Expressed, functional gene
Expressed, no known function

Direction of transcription
Pseudogene

LCR

Locus control region

Figure 6.2. Human -globin, and growth hormone gene clusters illustrating

relative locations of nonprocessed pseudogenes.

-globin,