PMID- 10408774
OWN - NLM
STAT- MEDLINE
DCOM- 19991103
LR  - 20071114
IS  - 1059-7794 (Print)
IS  - 1059-7794 (Linking)
VI  - 13
IP  - 6
DP  - 1999
TI  - Four novel mutations in the cystathionine beta-synthase gene: effect of a second 
      linked mutation on the severity of the homocystinuric phenotype.
PG  - 453-7
AB  - Homocystinuria due to cystathionine beta-synthase (CBS) deficiency is frequently 
      caused by missense mutations. In this article, we report four novel missense
      mutations in the CBS gene: 172C-->T (R58W) linked in cis with A114V; 376A-->G
      (M126V); 904G-->A (E302K); and 1006C-->T (R336C). The CBS activity of the
      corresponding mutant enzymes expressed in Escherichia coli was greatly
      diminished, confirming the pathogenicity of these mutations. Western analysis
      showed that the R58W+A114V and M126V mutant enzymes were unstable in E. coli,
      while the E302K subunits were partially degraded to shorter products. Using
      site-directed mutagenesis we found that CBS containing either the R58W or A114V
      as the only mutations demonstrated 18% and 46% of normal activity, respectively. 
      Both mutant forms of CBS were stable in E. coli. When these two mutations were
      expressed in cis, the resultant mutant protein exhibited activity 1.3% that of a 
      control. All these in vitro results were in good agreement with the clinical
      manifestation in these patients. The Italian patient 2241, an A114V+R58W/M126V
      compound heterozygote, exhibited severe pyridoxine nonresponsive homocystinuria, 
      while another Italian patient 2242, with an A114V/E302K genotype, responded to
      pyridoxine treatment and had a much milder phenotype. The third patient 3064, an 
      English compound heterozygote for two severe mutations R336C and G307S, was B6
      nonresponsive. This report of a ninth homocystinuric allele carrying two
      mutations in cis raises the possibility that double mutant alleles may be
      underestimated in homocystinuric patients. In this context, a search for
      additional mutations in cis may sometimes be necessary to establish a good
      genotype-phenotype relationship.
FAU - de Franchis, R
AU  - de Franchis R
AD  - Department of Pediatrics, University of Colorado School of Medicine, Denver, USA.
FAU - Kraus, E
AU  - Kraus E
FAU - Kozich, V
AU  - Kozich V
FAU - Sebastio, G
AU  - Sebastio G
FAU - Kraus, J P
AU  - Kraus JP
LA  - eng
GR  - 1R03TW00989-01/TW/FIC NIH HHS/United States
PT  - Journal Article
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - Hum Mutat
JT  - Human mutation
JID - 9215429
RN  - EC 4.2.1.22 (Cystathionine beta-Synthase)
SB  - IM
MH  - Alleles
MH  - Child
MH  - Child, Preschool
MH  - Cystathionine beta-Synthase/*genetics/metabolism
MH  - Female
MH  - Fibroblasts
MH  - Genotype
MH  - Homocystinuria/*genetics
MH  - Humans
MH  - Male
MH  - Mutagenesis
MH  - *Mutation
MH  - Phenotype
EDAT- 1999/07/17 10:00
MHDA- 2000/06/22 10:00
CRDT- 1999/07/17 10:00
PHST- 1999/07/17 10:00 [pubmed]
PHST- 2000/06/22 10:00 [medline]
PHST- 1999/07/17 10:00 [entrez]
AID - 10.1002/(SICI)1098-1004(1999)13:6<453::AID-HUMU4>3.0.CO;2-K [pii]
AID - 10.1002/(SICI)1098-1004(1999)13:6<453::AID-HUMU4>3.0.CO;2-K [doi]
PST - ppublish
SO  - Hum Mutat. 1999;13(6):453-7. doi:
      10.1002/(SICI)1098-1004(1999)13:6<453::AID-HUMU4>3.0.CO;2-K.