Requirement for basement membrane laminin α5 during urethral and external genital development

Abstract

Hypospadias, a congenital malformation of the penis characteristic of an abnormal urethral orifice, affects 1 in every 125 boys, and its incidence is rising. Herein we test the hypothesis that the basement membrane protein laminin α5 (LAMA5) plays a key role in the development of the mouse genital tubercle, the embryonic anlage of the external genitalia. Using standard histological analyses and electron microscopy, we characterized the morphology of the external genitalia in Lama5 knockout (LAMA5-KO) mouse embryos during both androgen-independent genital tubercle development and androgen-mediated sexual differentiation. We compared regulatory gene expression between control and LAMA5-KO by in situ hybridization. We also examined the epithelial structure of the mutant genital tubercle using immunofluorescence staining and histological analyses of semi-thin sections. We found that Lama5 was expressed in both ectodermal and endodermal epithelia of the cloaca. The LAMA5-KO displayed a profound external genital malformation in which the genital tubercle was underdeveloped with a large ectopic orifice at the proximal end. In older embryos, the urethra failed to form a tubular structure and was left completely exposed. These defects were not associated with a significant alteration in regulatory gene expression, but rather with a defective ectodermal epithelium and an abnormal disintegration of the cloacal membrane. We conclude that LAMA5 is required in the basement membrane to maintain normal architecture of the ventral ectoderm during genital tubercle development, which is essential for the formation of a tubular urethra. Perturbation of LAMA5, and possibly other basement membrane components, may cause hypospadias in humans.

Down-Regulation of Laminin (LN)- α5 is Associated with Preeclampsia and Impairs Trophoblast Cell Viability and Invasiveness Through PI3K Signaling Pathway

“…LN-α5 has been shown to be critical for vasculature remodeling and angiogenesis, which illustrates the important role of this receptor in modulating cell function [31]. It is expressed in embryonic development [10,32,33]; therefore, we speculated that LN-α5 might be involved in the regulation of trophoblast cell function during placentation. The aim of this study is to investigate the regulatory effects of LN-α5 on the biological functions of trophoblast cells.…”

Spatiotemporal map of key signaling factors during early penis development

“…At E12.5, Ptch1 localizes to the mesenchyme surrounding the urethra and UPE but with levels higher in the proximal mesenchyme and low in the dorsal and distal mesenchyme. 41 This expression pattern continues through E13.5, with a more complex pattern in the distal penis. For example, Ptch1 is expressed in a subset of the UPE cells as well as extensively in the mesenchyme, in particular concentrated in mesenchyme immediately underlying penile urethra and ectoderm.…”

Etiology of Hypospadias: A Comparative Review of Genetic Factors and Developmental Processes Between Human and Animal Models

“…Although distal urethral defects were observed in Bnc2 knockout newborn mice, 102 no urogenital abnormalities were present in Mid1 knockout mice, 113 and also no external genital phenotype has been reported in Cdh11 , 114 Dgkk , Haao , 115 Lsm1 , Myrf , Pkg2 , 116 or Irx6 knockout mice. In addition, Lama5 was found to be required for urethral and external genital development, and deletion of Lama5 induced hypospadias in mice, suggesting it may be a potential hypospadias causal gene; 117 until now, no SNP or mutation of LAMA5 has been reported in hypospadias patients ( Table 1 ).…”