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Drosophila melanogaster Cad99C, the orthologue of human Usher cadherin PCDH15, regulates the length of microvilli.

D'Alterio C, Tran DD, Yeung MW, Hwang MS, Li MA, Arana CJ, Mulligan VK, Kubesh M, Sharma P, Chase M, Tepass U, Godt D - J. Cell Biol. (2005)

Bottom Line: Loss of Cad99C function results in shortened and disorganized microvilli, whereas overexpression of Cad99C leads to a dramatic increase of microvillus length.Cad99C that lacks most of the cytoplasmic domain, including potential PDZ domain-binding sites, still promotes excessive microvillus outgrowth, suggesting that the amount of the extracellular domain determines microvillus length.This study reveals Cad99C as a critical regulator of microvillus length, the first example of a transmembrane protein that is involved in this process.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Toronto, Toronto, Ontario, Canada, M5S 3G5.

ABSTRACT
Actin-based protrusions can form prominent structures on the apical surface of epithelial cells, such as microvilli. Several cytoplasmic factors have been identified that control the dynamics of actin filaments in microvilli. However, it remains unclear whether the plasma membrane participates actively in microvillus formation. In this paper, we analyze the function of Drosophila melanogaster cadherin Cad99C in the microvilli of ovarian follicle cells. Cad99C contributes to eggshell formation and female fertility and is expressed in follicle cells, which produce the eggshells. Cad99C specifically localizes to apical microvilli. Loss of Cad99C function results in shortened and disorganized microvilli, whereas overexpression of Cad99C leads to a dramatic increase of microvillus length. Cad99C that lacks most of the cytoplasmic domain, including potential PDZ domain-binding sites, still promotes excessive microvillus outgrowth, suggesting that the amount of the extracellular domain determines microvillus length. This study reveals Cad99C as a critical regulator of microvillus length, the first example of a transmembrane protein that is involved in this process.

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Eggs derived from Cad99C mutant females have a defective VM. (A) A wild-type D. melanogaster egg. (B) A collapsed egg from a Cad99C21-5 mutant female. (C) Eggs from Cad99C mutant mothers dehydrated over time. By mid-embryogenesis >90% of the eggs were collapsed. Eggs from the P insertion line GE21034, the progenitor of the Cad99C mutant lines, did not collapse. Numbers of examined eggs: wild type (wt), n = 468; GE21034, n = 367; Cad99C21-5, n = 325; Cad99C21-8, n = 375; Cad99C21-9, n = 245. (D) Trypan blue did not penetrate wild-type eggs but stained to a variable degree eggs from Cad99C21-9 (E–G) and Cad99C21-5 (H) mutant mothers. In most eggs, the anterior region was stained strongest. (I) In contrast to normal eggs, 50% of the eggs from Cad99C mutants had disintegrated in sodium hydrochlorite after 30 min. The histogram shows mean values and SDs based on four experiments. (J and K) Histological sections of stage 11 egg chambers show that the VM is continuous in wild type (J) but has gaps in a Cad99C21-8 mutant follicle (K, arrows). Oc, oocyte; Fc, follicle cells.
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fig3: Eggs derived from Cad99C mutant females have a defective VM. (A) A wild-type D. melanogaster egg. (B) A collapsed egg from a Cad99C21-5 mutant female. (C) Eggs from Cad99C mutant mothers dehydrated over time. By mid-embryogenesis >90% of the eggs were collapsed. Eggs from the P insertion line GE21034, the progenitor of the Cad99C mutant lines, did not collapse. Numbers of examined eggs: wild type (wt), n = 468; GE21034, n = 367; Cad99C21-5, n = 325; Cad99C21-8, n = 375; Cad99C21-9, n = 245. (D) Trypan blue did not penetrate wild-type eggs but stained to a variable degree eggs from Cad99C21-9 (E–G) and Cad99C21-5 (H) mutant mothers. In most eggs, the anterior region was stained strongest. (I) In contrast to normal eggs, 50% of the eggs from Cad99C mutants had disintegrated in sodium hydrochlorite after 30 min. The histogram shows mean values and SDs based on four experiments. (J and K) Histological sections of stage 11 egg chambers show that the VM is continuous in wild type (J) but has gaps in a Cad99C21-8 mutant follicle (K, arrows). Oc, oocyte; Fc, follicle cells.

Mentions: The female-sterile phenotype of Cad99C mutants is caused by defects in eggshell formation as revealed by the following analysis. Cad99C21-5, Cad99C21-8, or Cad99C21-9 mutant females laid ∼50% fewer eggs than wild-type females, and <2% of those eggs (n > 300 per genotype) produced larvae. These larvae developed into flies that only displayed defects if they were homozygous mutants, and those defects are the same as in homozygous mutants derived from heterozygous mothers, suggesting that maternal loss of Cad99C has no effect on postembryonic development. The majority of eggs from Cad99C mutant females collapsed soon after deposition (Fig. 3, A–C), and even noncollapsed eggs were penetrable to the vital dyes neutral red and trypan blue (Fig. 3, D–H), which do not stain wild-type eggs (Mahowald, 1972; LeMosy and Hashimoto, 2000). These defects suggested that eggshells, which normally restrict permeability and prevent desiccation (Limbourg and Zalokar, 1973; Mahowald and Kambysellis, 1980), are compromised. Eggs from mutant females were also highly intolerant to sodium hydrochlorite. Hydrochlorite treatment of wild-type eggs removes the outer eggshell, the chorion, but leaves the inner eggshell, the vitelline membrane (VM), intact (Limbourg and Zalokar, 1973). Disintegration of eggs from Cad99C mutant females in hydrochlorite suggests that the VM is not functional (Fig. 3 I). The VM normally forms a continuous layer of homogeneous thickness in late follicles (Mahowald and Kambysellis, 1980), whereas the VM of Cad99C mutant follicles varied in thickness and contained numerous holes (Fig. 3, J and K). These holes are likely the cause for the observed desiccation of eggs. The variability in eggshell defects may explain why mutant females are not fully sterile, allowing a few embryos to develop. The importance of Cad99C for proper eggshell formation is consistent with its expression in follicle cells that secrete the eggshell material.


Drosophila melanogaster Cad99C, the orthologue of human Usher cadherin PCDH15, regulates the length of microvilli.

D'Alterio C, Tran DD, Yeung MW, Hwang MS, Li MA, Arana CJ, Mulligan VK, Kubesh M, Sharma P, Chase M, Tepass U, Godt D - J. Cell Biol. (2005)

Eggs derived from Cad99C mutant females have a defective VM. (A) A wild-type D. melanogaster egg. (B) A collapsed egg from a Cad99C21-5 mutant female. (C) Eggs from Cad99C mutant mothers dehydrated over time. By mid-embryogenesis >90% of the eggs were collapsed. Eggs from the P insertion line GE21034, the progenitor of the Cad99C mutant lines, did not collapse. Numbers of examined eggs: wild type (wt), n = 468; GE21034, n = 367; Cad99C21-5, n = 325; Cad99C21-8, n = 375; Cad99C21-9, n = 245. (D) Trypan blue did not penetrate wild-type eggs but stained to a variable degree eggs from Cad99C21-9 (E–G) and Cad99C21-5 (H) mutant mothers. In most eggs, the anterior region was stained strongest. (I) In contrast to normal eggs, 50% of the eggs from Cad99C mutants had disintegrated in sodium hydrochlorite after 30 min. The histogram shows mean values and SDs based on four experiments. (J and K) Histological sections of stage 11 egg chambers show that the VM is continuous in wild type (J) but has gaps in a Cad99C21-8 mutant follicle (K, arrows). Oc, oocyte; Fc, follicle cells.
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Related In: Results  -  Collection

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fig3: Eggs derived from Cad99C mutant females have a defective VM. (A) A wild-type D. melanogaster egg. (B) A collapsed egg from a Cad99C21-5 mutant female. (C) Eggs from Cad99C mutant mothers dehydrated over time. By mid-embryogenesis >90% of the eggs were collapsed. Eggs from the P insertion line GE21034, the progenitor of the Cad99C mutant lines, did not collapse. Numbers of examined eggs: wild type (wt), n = 468; GE21034, n = 367; Cad99C21-5, n = 325; Cad99C21-8, n = 375; Cad99C21-9, n = 245. (D) Trypan blue did not penetrate wild-type eggs but stained to a variable degree eggs from Cad99C21-9 (E–G) and Cad99C21-5 (H) mutant mothers. In most eggs, the anterior region was stained strongest. (I) In contrast to normal eggs, 50% of the eggs from Cad99C mutants had disintegrated in sodium hydrochlorite after 30 min. The histogram shows mean values and SDs based on four experiments. (J and K) Histological sections of stage 11 egg chambers show that the VM is continuous in wild type (J) but has gaps in a Cad99C21-8 mutant follicle (K, arrows). Oc, oocyte; Fc, follicle cells.
Mentions: The female-sterile phenotype of Cad99C mutants is caused by defects in eggshell formation as revealed by the following analysis. Cad99C21-5, Cad99C21-8, or Cad99C21-9 mutant females laid ∼50% fewer eggs than wild-type females, and <2% of those eggs (n > 300 per genotype) produced larvae. These larvae developed into flies that only displayed defects if they were homozygous mutants, and those defects are the same as in homozygous mutants derived from heterozygous mothers, suggesting that maternal loss of Cad99C has no effect on postembryonic development. The majority of eggs from Cad99C mutant females collapsed soon after deposition (Fig. 3, A–C), and even noncollapsed eggs were penetrable to the vital dyes neutral red and trypan blue (Fig. 3, D–H), which do not stain wild-type eggs (Mahowald, 1972; LeMosy and Hashimoto, 2000). These defects suggested that eggshells, which normally restrict permeability and prevent desiccation (Limbourg and Zalokar, 1973; Mahowald and Kambysellis, 1980), are compromised. Eggs from mutant females were also highly intolerant to sodium hydrochlorite. Hydrochlorite treatment of wild-type eggs removes the outer eggshell, the chorion, but leaves the inner eggshell, the vitelline membrane (VM), intact (Limbourg and Zalokar, 1973). Disintegration of eggs from Cad99C mutant females in hydrochlorite suggests that the VM is not functional (Fig. 3 I). The VM normally forms a continuous layer of homogeneous thickness in late follicles (Mahowald and Kambysellis, 1980), whereas the VM of Cad99C mutant follicles varied in thickness and contained numerous holes (Fig. 3, J and K). These holes are likely the cause for the observed desiccation of eggs. The variability in eggshell defects may explain why mutant females are not fully sterile, allowing a few embryos to develop. The importance of Cad99C for proper eggshell formation is consistent with its expression in follicle cells that secrete the eggshell material.

Bottom Line: Loss of Cad99C function results in shortened and disorganized microvilli, whereas overexpression of Cad99C leads to a dramatic increase of microvillus length.Cad99C that lacks most of the cytoplasmic domain, including potential PDZ domain-binding sites, still promotes excessive microvillus outgrowth, suggesting that the amount of the extracellular domain determines microvillus length.This study reveals Cad99C as a critical regulator of microvillus length, the first example of a transmembrane protein that is involved in this process.

View Article: PubMed Central - PubMed

Affiliation: Department of Zoology, University of Toronto, Toronto, Ontario, Canada, M5S 3G5.

ABSTRACT
Actin-based protrusions can form prominent structures on the apical surface of epithelial cells, such as microvilli. Several cytoplasmic factors have been identified that control the dynamics of actin filaments in microvilli. However, it remains unclear whether the plasma membrane participates actively in microvillus formation. In this paper, we analyze the function of Drosophila melanogaster cadherin Cad99C in the microvilli of ovarian follicle cells. Cad99C contributes to eggshell formation and female fertility and is expressed in follicle cells, which produce the eggshells. Cad99C specifically localizes to apical microvilli. Loss of Cad99C function results in shortened and disorganized microvilli, whereas overexpression of Cad99C leads to a dramatic increase of microvillus length. Cad99C that lacks most of the cytoplasmic domain, including potential PDZ domain-binding sites, still promotes excessive microvillus outgrowth, suggesting that the amount of the extracellular domain determines microvillus length. This study reveals Cad99C as a critical regulator of microvillus length, the first example of a transmembrane protein that is involved in this process.

Show MeSH
Related in: MedlinePlus