In vitro transcription of compound heterozygous hypofibrinogenemia Matsumoto IX; first identification of FGB IVS6 deletion of 4 nucleotides and FGG IVS3-2A>G causing abnormal RNA splicing.
BACKGROUND
We reported a case of hypofibrinogenemia Matsumoto IX (M IX) caused by a novel compound heterozygous mutation involving an FGB IVS6 deletion of 4 nucleotides (Delta4b) (three T, one G; between FGB IVS6-10 and -16) and FGG IVS3-2A/G, which are both identified for the first time. To examine the transcription of mRNA from the M IX gene, we cloned the wild-type and mutant genes into expression vectors.


METHODS
The vectors were transfected into CHO cells and transiently produced wild-type, Bbeta- or gamma-mRNA in the cells. The mRNAs amplified with RT-PCR were analyzed by agarose gel electrophoresis and nucleotide sequencing.


RESULTS
The RT-PCR product from FGB IVS6Delta4b showed aberrant mRNA that included both introns 6 and 7, and that from FGG IVS3-2G showed two aberrant mRNAs, a major one including intron 3 and a minor in which intron 3 was spliced by a cryptic splice site in exon 4. We speculated that the aberrant mRNAs are degraded before translation into proteins, and/or translated variant chains are subjected to quality control and degraded in the cytoplasm.


CONCLUSIONS
The reduced plasma fibrinogen level of the M IX patient was caused by abnormal RNA splicing of one or both of the FGB and FGG genes.
Terasawa
Fumiko
F
Department of Biomedical Laboratory Sciences, School of Health Sciences, Shinshu University, 3-1-1 Asahi, Matsumoto, 390-8621, Japan. fterasa@shinshu-u.ac.jp
Kamijyo
Yuka
Y
Fujihara
Noriko
N
Yamauchi
Kazuyoshi
K
Kumagai
Toshiko
T
Honda
Takayuki
T
Shigematsu
Satoshi
S
Okumura
Nobuo
N
D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D017931:DNA Primers; D015241:Fibrinogens, Abnormal / Q000235:genetics* / Q000378:metabolism; D006579:Heterozygote; D006801:Humans; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D014158:Transcription, Genetic
D017931:DNA Primers; D015241:Fibrinogens, Abnormal; D012333:RNA, Messenger