Biology Reference
In-Depth Information
channel genes many of which reside in the same paralogous chromosome seg-
ments as the HOX gene clusters:
SCN1A, SCN2A, SCN3A, SCN6A, SCN7A
and
SCN9A
(2q23-q24),
SCN8A
(12q13),
SCN4A
(17q23-q25),
SCN5A
and
SCN10A
(3p21-p24) (Plummer and Meisler, 1999).
By contrast the localized duplication of translocated genes appears to be a gen-
eral feature of the human olfactory receptor (
OLFR
) genes (Trask
et al
., 1998b).
Thus, several
OLFR
gene clusters on chromosome 11 (11p15, 11p13, 11q24;
Buettner
et al
., 1998) are more similar to each other than to
OLFR
genes on chro-
mosome 17 (Ben-Arie
et al
., 1994), implying that translocation was followed by
regional tandem duplication. However, the
OLFR
gene cluster on chromosome
17p13.3 contains members that do not belong to the same subfamily, suggesting
that it originated instead by duplication of an entire gene cluster followed by
translocation of that cluster (Ben-Arie
et al
., 1994).
8.5.6 Syntenic relationships and gene dispersal
Gene duplication sometimes creates gene families whose members are both syn-
tenic and dispersed, for example the human purinoceptor gene family (
P2RY1
, 3;
P2RY2
, 11q13.5-q14.1;
P2RY4
, Xq13;
P2RY6
, 11q13.5,
P2RY7
, chromosome 14;
Somers
et al
., 1997). Seven human matrix metalloproteinase genes cluster at chro-
mosome 11q22.3 (
MMP1
,
MMP3
,
MMP7
,
MMP8
,
MMP10
,
MMP12
,
MMP13
;
Pendas
et al
., 1996), but the other family members are dispersed between many
other chromosomes (
MMP2
, 16q13;
MMP9
, 20q11.2-q13.1;
MMP11
, 22q11.2;
MMP14
, 14q11-q12;
MMP15
, 16q21;
MMP16
, 8q21;
MMP19
, 12q14). Other
examples include the human fucosyltransferase (
FUT1
,
FUT2
,
FUT3
,
FUT5
,
FUT6
, 19p13.3;
FUT4
, 11q21;
FUT7
, 9q34;
FUT8
, 14q23; Costache
et al
., 1997)
and annexin genes (
ANX1
, 9q11-q22;
ANX2
, 15q21-q22;
ANX3
, 4q13-q22;
ANX4
, 2p13;
ANX5
, 4q28-q32;
ANX6
, 5q32-q34;
ANX7
, 10q21.1-q21.2;
ANX8
,
10q11.2;
ANX11
, 10q21.1-q21.2;
ANX13
, 8q24.1-q24.2; Morgan
et al
., 1998).
In some cases, evolutionary conservation of post-duplicational clustering may
be important for the coordinate regulation of individual genes by common con-
trol elements (see Chapter 5, section 5.1.14). Possible examples of this include the
spermatid-specific protamine (
PRM1
and
PRM2
; 16p13.2) genes (Nelson and
Krawetz, 1994), the platelet membrane glycoprotein (
ITGA2B
and
ITGA3
;
17q21-q22) genes (Bray
et al
., 1988), the albumin gene family (
ALB
,
AFP
,
AFM
,
GC
; 4q11-q13; Nishio
et al
., 1996), the pregnancy-specific glycoprotein (
PSG1
,
PSG2
,
PSG3
,
PSG4
,
PSG5
,
PSG6
,
PSG7
,
PSG8
,
PSG11
,
PSG12
,
PSG13
;
19q13.2) genes (Khan
et al
., 1992) and the fibrinogen
,
and
(
FGA
,
FGB
and
FGG
; 4q31) genes (Fu
et al
., 1992; Roy
et al
., 1994).
Individually duplicated genes may still exhibit synteny simply because recom-
bination has not yet separated them. Thus, the paralogous pulmonary surfactant
protein D (
SFTPD
) gene at 10q22-q23 lies in very close proximity to the pul-
monary surfactant protein A (
SFTPA1
) gene (Kölble
et al
., 1993). Similarly, the
paralogous the interferon
receptor gene (
IFNAR1
) is closely linked to the
cytokine receptor B4 (
CRFB4
) gene on chromosome 21q22.1 (Lutfalla
et al
.,
1995). Synteny may however be retained for very long periods of evolutionary
time. Indeed, the human proteasome
α/β
2 subunit (
PSMA2
) and TATA box-bind-
