These results demonstrate that, in the B6C3F1 mouse TL, X-ray-induced lymphomagenesis showed both the co-expression, yet low occurrence of allelic imbalance on chromosome 6 and K-ras mutation, and exclusive expression of frequent allelic imbalance on chromosomes 4, 11 and 12 and K-ras mutation.
We systematically investigated the molecular defects causing a primary LPL deficiency in a Japanese male infant (patient DI) with fasting hyperchylomicronemia (type I hyperlipoproteinemia) and in his parents. Patient DI had neither LPL activity nor immunoreactive LPL mass in the pre-and post-heparin plasma. The patient was a compound heterozygote for novel mutations consisting of a G-to-T transversion at the first nucleotide of exon 5 [ ؉ 1 position of 3 Ј acceptor splice site (3 Ј -ass) of intron 4] and a T-to-C transition in the invariant GT at position ؉ 2 of the 5 Ј donor splice site (5´-dss) of intron 8 (Int8/5 Ј -dss/t( ؉ 2)c). The G-to-T transversion, although affecting the 11 nucleotide of the 3 Ј -consensus acceptor splice site, resulted in a substitution of Gly 154 to Val (G154V; GG 716 C → GTC). The mutant G154V LPL expressed in COS-1 cells was catalytically inactive and hardly released from the cells by heparin. The Int8/5 Ј -dss/t( ؉ 2)c mutation inactivated the authentic 5 Ј splice site of intron 8 and led to the utilization of a cryptic 5 Ј -dss in exon 8 as an alternative splice site 133 basepairs upstream from the authentic splice site, thereby causing joining of a part of exon 8 to exon 9 with skipping of a 134-bp fragment of exon 8 and intron 8. These additional mutations in the consensus sequences of the 3 Ј and 5 Ј splice sites might be useful for better understanding the factors that are involved in splice site selection in vivo. -Ikeda, Y., A.
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