Neuronal ceroid lipofuscinosis genes, CLN2, CLN3 and CLN5 are spatially and temporally co-expressed in a developing mouse brain

Neuronal ceroid lipofuscinosis (NCL) diseases consist of a group of genetically inherited neurodegenerative disorders that share common symptoms such as seizures, psychomotor retardation, blindness, and premature death. Although gene defects behind the NCL diseases are well characterized, very little is known how these defects affect normal development of the brain and cause the pathology of the disease. To obtain understanding of the development of the cell types that are mostly affected by defective function of CLN proteins, timing of expression of CLN2, CLN3 and CLN5 genes was investigated in developing mouse brain. The relationship between the expression pattern and the developmental stage of the brain showed that these genes are co-expressed spatially and temporally during brain development. Throughout the development strong expression of the three mRNAs was detected in germinal epithelium and in ventricle regions, hippocampus and cerebellum, all representing regions that are known to be associated with the formation of new neurons. More specifically, RT-PCR studies on developing mouse cortices revealed that the CLN genes were temporally co-expressed in the neural progenitor cells together with known stem cell markers. This suggested that CLN2, CLN3 and CLN5 genes may play an important role in early embryonal neurogenesis.

A linear RNA replicon from the oomycete Phytophthora infestans

An unusual RNA element was discovered in an isolate of the oomyceteous fungus Phytophthora infestans. The RNA exists predominantly as single-stranded molecules of about 625 nucleotides with complementary strands present at a ratio of approximately 130:1. Gel mobility and PCR assays indicated that the element was linear. The RNA appeared to be an autonomous element, since P. infestans DNA did not contain cross-hybridizing sequences. Standard methods for virus purification yielded no evidence for encapsidation of the RNA, or for other virus particles in the isolate bearing the replicon. The replicon contained polyU and polyA tracts at its 5' and 3' termini, respectively, with a central region that had a GC content of 47%, and lacked obvious ORFs. Two-thirds of the replicon co-purified with nuclei, at about 200 copies per nucleus, while one-third resided in a cytoplasmic but non-mitochondrial location. Maternal inheritance was observed in sexual crosses, with a few exceptions. The replicon was not widely distributed throughout the species and had little effect on growth or pathogenicity. The data suggest that the RNA is best characterized as a novel linear RNA plasmid.

Genetic Analysis of Metalaxyl Insensitivity Loci in Phytophthora infestans Using Linked DNA Markers

ABSTRACT Previous studies indicated that incompletely dominant loci determine insensitivity by oomycetes to phenylamide fungicides such as metalaxyl. To compare the bases of insensitivity in different strains of the late blight pathogen, Phytophthora infestans, crosses were performed between sensitive isolates and isolates from Mexico, the Netherlands, and the United Kingdom that displayed varying levels of insensitivity. Segregation analyses indicated that metalaxyl insensitivity was determined primarily by one locus in each isolate, and that two of the isolates were heterozygous and the other homozygous for the insensitive allele. Metalaxyl insensitivity was also affected by the segregation of additional loci of minor effect. DNA markers linked to insensitivity were obtained by bulked segregant analysis using random amplified polymorphic DNA (RAPD) markers and the Dutch and Mexican crosses. By studying the linkage relationships between these markers and the insensitivity in each cross by RAPD or restriction fragment length polymorphism analysis, it appeared that the same chromosomal locus conferred insensitivity in the Mexican and Dutch isolates. However, a gene at a different chromosomal position was responsible for insensitivity in the British isolate.

Mating-type loci segregate aberrantly in Phytophthora infestans but normally in Phytophthora parasitica: implications for models of mating-type determination

In the oomycete, Phytophthora infestans, mating type is determined by a locus that segregates in a non-Mendelian manner consistent with its linkage to a system of balanced lethals. The significance of this unusual phenomenon was addressed by studying the segregation patterns of DNA markers linked to mating type in the related species, P. parasitica. This was done using loci identified by either RAPD analysis of P. parasitica crosses or by cross-hybridization with RFLP markers linked to mating type in P. infestans. The resulting data revealed that, unlike P. infestans, mating type in P. parasitica was regulated by a locus displaying Mendelian segregation. An improved model for mating-type determination in Phytophthora is presented.