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From the Division of Pathology,* Hospital for Sick Children, Toronto, Canada; the Division of Immunology, Shigei Medical Research Institute, Okayama, Japan; the Department of Pathobiology, University of Guelph, Guelph, Canada; the Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan; the Department of Medicine,¶ Vanderbilt University, Nashville, Tennessee; and the Department of Laboratory Medicine and Pathobiology,|| University of Toronto, Toronto, Canada
The six 
chains of type IV collagen are organized into three networks: 1/2, 3/4/5, and 1/2/5/6. A shift from the 1/2 to the 3/4/5 network occurs in the developing glomerular basement membrane, but how the 1/2/5/6 network fits into this sequence is less clear, because the three networks do not colocalize. Here, we studied the seminiferous tubule basement membrane of normal canine testis where all three networks do colocalize: the 1/2 network is expressed from birth, the 1/2/5/6 network by 5–6 weeks of age, and the 3/4/5 network by 2 months of age. A canine model of Alport syndrome allowed study of the absence of 3/4/5 and 1/2/5/6 networks in testis. In Alport dogs, the seminiferous tubule basement membrane was thinner than in controls. Spermatogenesis began at the same time as with normal dogs; however, the number of mature sperm was significantly reduced in Alport dogs. Thus, it would appear that 3/4/5 and 1/2/5/6 networks are not essential for onset of spermatogenesis, but long-term function may be compromised by the loss of one or both networks. This situation is analogous to the glomerular basement membrane in Alport syndrome. In conclusion, testis can serve as a model system to study the sequence of type IV collagen network expression.
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