Colorectal Cancers Mimic Structural Organization of Normal Colonic Crypts

Colonic crypts are stereotypical structures with distinct stem cell, proliferating, and differentiating compartments. Colorectal cancers derive from colonic crypt epithelia but, in contrast, form morphologically disarrayed glands. In this study, we investigated to which extent colorectal cancers phenocopy colonic crypt architecture and thus preserve structural organization of the normal intestinal epithelium. A subset of colon cancers showed crypt-like compartments with high WNT activity and nuclear β-Catenin at the leading tumor edge, adjacent proliferation, and enhanced Cytokeratin 20 expression in most differentiated tumor epithelia of the tumor center. This architecture strongly depended on growth conditions, and was fully reproducible in mouse xenografts of cultured and primary colon cancer cells. Full crypt-like organization was associated with low tumor grade and was an independent prognostic marker of better survival in a collection of 221 colorectal cancers. Our findings suggest that full activation of preserved intestinal morphogenetic programs in colon cancer requires in vivo growth environments. Furthermore, crypt-like architecture was linked with less aggressive tumor biology, and may be useful to improve current colon cancer grading schemes.     

Performance of non-motile male gametes in the sea: analysis of paternity and fertilization success in a natural population of a red seaweed,Gracilaria gracilis

In haploid–diploid red seaweeds, the dispersal of male gametes is presumed limited due to their lack of flagella. It has been suggested that this group suffers from sperm limitation and, consequently, that fertilization is relatively inefficient. Fertilization in most floridean rhodophytes results in the formation a cystocarp, a swelling on the haploid female thallus housing the diploid zygote and its thousands of diploid daughter spores. To study the performance of non-motile male gametes in the sea, we evaluated both female and male fertilization success in a natural population of the red marine alga Gracilaria gracilis. Female fertilization success, estimated by cystocarp yield per unit female thallus, was evaluated with respect to the availability of male gametes. Male fertilization success, estimated by the individual contribution of different males to zygotes, was assessed by paternity analyses on 350 cystocarps produced in one reproductive season using two microsatellite loci. The results show that cystocarp yield is not sperm limited and that the large variation in male fertilization success cannot be solely explained by the distance travelled by the male gamete to find a mate. Taken together, the results suggest that, not only is fertilization efficient, but that male–male competition and/or female choice may play a role in shaping population mating patterns.     

Plasmid transformation of Streptomyces tendae after heat attenuation of restriction

Streptomyces tendae ATCC 31160 produces nikkomycin, a fungicide and insecticide that inhibits chitin synthases. Exposure of S. tendae protoplasts to 50 degrees C for 30 min is required for transformation (10(2) thiostrepton-resistant transformants micrograms of DNA-1) with plasmid pIJ702 or pIJ680 from Streptomyces lividans. pIJ702 and pIJ680 DNA isolated from the S. tendae transformants is efficient (10(6) to 10(7) transformants micrograms of DNA-1) in subsequent transformations of S. tendae protoplasts generated at 30 degrees C. PstI fails to cut the single PstI site in pIJ702 and cuts only one of the two PstI sites in pIJ680 DNA isolated from S. tendae transformants. Digests of plasmid DNA mixtures showed that plasmid DNA from S. tendae does not inhibit PstI activity. pIJ702 and pIJ680 DNA from S. tendae transformants was used to transform S. lividans to show that plasmid DNA remains unchanged, except for modification at some PstI sites in S. tendae, as a consequence of passage through S. tendae. The DNA modification is lost when S. lividans is transformed with plasmid DNA from S. tendae transformants. Since S. tendae modifies only some PstI sites, it appears the modification (presumably restriction activity also) activity in S. tendae recognizes a sequence that includes or overlaps the PstI hexanucleotide recognition sequence.     

EGF-like domains in extracellular matrix proteins: localized signals for growth and differentiation?

Multidomain proteins of the extracellular matrix (ECM) play an important role in development and maintenance of cellular organization and in tissue repair. Several ECM proteins such as laminin, tenascin and thrombospondin contain domains with homology to epidermal growth factor (EGF) and exhibit growth promoting activity. The mitogenic activity of laminin is restricted to a fragment which consists of about 25 repeating domains with partial homology to EGF and comprises the rod-like inner regions of the three short arms of the four armed molecule. The mitogenic activity does not correlate with promotion of cell attachment and neurite outgrowth for which major functional sites have been found in other regions of the laminin molecule. It is suggested that EGF-like domains in laminin, in other ECM proteins and in the extracellular portions of some membrane proteins are signals for cellular growth and differentiation. Because they are integral parts of large molecules and often of supramolecular assemblies these domains are well suited to stimulate neighboring cells in a specific and vectorial way. This concept of localized growth or differentiation signals offers an attractive mechanism for the regulation of cellular development.