FIG. 1.

Construction of the targeting vector and generation of peri^lacZ knock-in mice. (A) The targeted mouse locus (top line) flanking exons 1, 2, and 3 are shown. A promoterless IRES-lacZ-neo-loxP cassette was inserted into exon 1 in the targeting construct (middle line), and the resulting targeted allele is shown (bottom line). TK, thymidine kinase. Both Southern blotting (B) and PCR genotyping (C) were used to identify the correctly targeted ES clones and to genotype the +/+, +/−, and peri^lacZ null mice. (D) Western blot analysis of periostin protein revealed that there is a complete absence of periostin expression in the newborn nulls and that the heterozygous mutants express only ∼30 to 50% of the normal levels of periostin protein. (E and F) Whole-embryo staining of lacZ expression in E14 heterozygous and E16 peri^lacZ null mice. Note widespread expression, particularly within the peripheral nervous system, craniofacial region, dermis of the skin, and body cavities. However, lacZ expression is absent in the fetal liver and restrictively expressed in the central nervous system, as staining is only within the olfactory lobe and the choroid plexus (F).