ABSTRACT. Patterning of the limb anterior-posterior axes depends on several signals that derive from the three signaling centers of the limb bud. These signals interact to constitute a complex and ordered network that critically contributes to the development of limb buds. Preaxial polydactyly in mouse is predominantly caused by ectopic expression of the zone of polarizing activity or Sonic hedgehog in the anterior region of the limb bud. In this study, we describe an N-ethyl-N-nitrosourea-induced polydactylous mouse ( Alx4 m1Yzcm ) with an extra digit on the anterior aspect of one or two hinddigits. The mutation was mapped to chromosome 2, between markers D2Mit45 and D2Mit184. The Alx4 gene was identified as a potential candidate gene in this location. Sequence analysis of the Alx4 gene for polydactylous heterozygotes revealed an A/T transversion mutation that resulted in substitution of a lysine codon with a stop (nonsense) codon at position 145. Alx4 m1Yzcm homozygous mice exhibited multiple abnormalities, including extensive preaxial polydactyly of all four limbs (up to seven digits) and the formation of omphalocele.

NADPH is an essential factor for Fatty Acid (FA) biosynthesis. The effect of NADPH generating enzymes [NADP +-dependent malic enzyme (NADP-ME), NADP +-dependent isocitrate dehydrogenase (NADP-IDH), Glucose 6-Phosphate Dehydrogenase (GPD) and 6-Phosphogluconate Dehydrogenase (PGD)] on FA biosynthesis was investigated in an engineered Escherichia coli BL21 △fadE/pTE. Among NADPH-generating enzymes, GPD and ICD increased total FA production by 60 and 16% respectively. Especially medium-chain FA production was increased up to 4.2 and 2.5 folds respectively. In addition, overexpression of the endogenous Thioesterase (TE) reduced Cyclopropane Fatty Acid (CFA) production by 40% and over-expressing of GPD and ICD further decreased CFA production by 23 and 30%, respectively compared to the TE overexpressed strain. Over-expression of TE appeared to be a good strategy to produce high quality biodiesel with medium-chain FAs as major Component (62%) and with Minimal Amount of CFA (4%). This study reveals that NADPHgenerating enzyme GPD is associated with FA biosynthesis in E. coli, but not all reducing power generating enzymes, are involved in FA biosynthesis in bacteria.

Peutz-Jeghers syndrome (PJS) is an autosomal dominantly inherited disease characterized by multiple gastrointestinal hamartomatous polyps and melanin spots on lips and buccal mucosa, with an increased risk for various cancers. The PJS gene, a potential tumour suppressor gene, encoding a serine/ threonie kinase (STK ll ), was mapped to chromosome 19pI3.3. To investigate the mutations of STK ll gene in Chinese with PJS, we analyzed its coding sequence in fifteen patients and twenty unaffected members of six families, including three multigenerational families with PJS and three sporadic families with PJS, by PCR, PCR-DHPLC and DNA sequencing techniques. Ten point mutations were found in the six families, including five missense mutations, one acceptor-splice site mutation, a nonsense mutation and three silent mutations. Our data showed that five missense mutations occurrd at codon 123 (CAG to CAT) in exon 2, codon 161 (ATT to AGT) in exon 4, codon 194 (GAC to GAG) in exon 4, codon 245 (CTC to TTC) in exon 5 and codon 354 (TTC to TTG) in exon 8. One kind of nonsense mutation was detected at codon 37 (CAG to TAG) in exon 1. Furthermore, we found an intronic mutation at a splice-acceptor site: a one base substitution from AG to AA in intron 4. These mutations were not detected in 20 normal DNA samples. In three sporadic families, only in one patient, we detected a missense mutation in exon 5. In addition, we found three silent mutations, which may cause polymorphisms of STK ll gene in introns 1(+36),3(-51) and 5(+27). These results indicated that the point mutation in STK ll might be involved in PJS pathogenesis. Mutation frequency is higher in the families suffering PJS in three or more generations than that of the sporadic cases.