PTPRF is disrupted in a patient with syndromic amastia

Abstract

Background: The presence of mammary glands distinguishes mammals from other organisms. Despite significant advances in defining the signaling pathways responsible for mammary gland development in mice, our understanding of human mammary gland development remains rudimentary. Here, we identified a woman with bilateral amastia, ectodermal dysplasia and unilateral renal agenesis. She was found to have a chromosomal balanced translocation, 46,XX,t(1;20)(p34.1;q13.13). In addition to characterization of her clinical and cytogenetic features, we successfully identified the interrupted gene and studied its consequences.

Methods: Characterization of the breakpoints was performed by molecular cytogenetic techniques. The interrupted gene was further analyzed using quantitative real-time PCR and western blotting. Mutation analysis and high-density SNP array were carried out in order to find a pathogenic mutation. Allele segregations were obtained by haplotype analysis.

Results: We enabled to identify its breakpoint on chromosome 1 interrupting the protein tyrosine receptor type F gene (PTPRF). While the patient's mother and sisters also harbored the translocated chromosome, their non-translocated chromosomes 1 were different from that of the patient. Although a definite pathogenic mutation on the paternal allele could not be identified, PTPRF's RNA and protein of the patient were significantly less than those of her unaffected family members.

Conclusions: Although ptprf has been shown to involve in murine mammary gland development, no evidence has incorporated PTPRF in human organ development. We, for the first time, demonstrated the possible association of PTPRF with syndromic amastia, making it a prime candidate to investigate for its spatial and temporal roles in human breast development.

Figure 1

Clinical features of the proband. (A) Face shows absence of all four upper incisors (small, brown and easily decayed) after extraction at age 15 years, epicanthal folds, and small cup-shaped pinnae. (B) Computerized tomography of kidneys shows absence of the left kidney and its renal artery.

Figure 2

Karyotype, FISH, and the breakpoint on chromosome 1. (A) Partial karyotype shows apparently reciprocal balanced translocation of 1p34.1 and 20q13.13. (B) Fluorescence in situ hybridization using RP5-1029K14 labeled in red with spectrum orange dUTP, shows hybridization signals on both derivative chromosomes indicating that this probe encompasses the breakpoint. The 1p subtelomeric probe labeled with spectrum green dUTP indicates chromosome 1. (C) Schematic presentation of the clones and genes in the 1p34.1 region, modified from the NCBI Map Viewer http://www.ncbi.nlm.nih.gov/mapview. Three ~10 kb probes are shown in green numbered from left to right, BAC/PAC contigs covering the 1p34.1 breakpoint are shown in purple. The orange dotted lines indicate the critical region.

Figure 3

Expression studies of the PTPRF. (A) Relative quantification using 5'PTPRF probe (proximal to the breakpoint) showed that the expression level in the proband was significantly decreased compared with that in a control, the proband's mother and sister. (B) Relative quantification using the 3'PTPRF probe (distal to the breakpoint) showed significantly decreased expression in the proband. Data are presented as mean ± SEM. ** indicates P < 0.01 (independent 1-tailed t-test) using GAPDH as a control. (C) Western blot analysis showing levels of the PTPRF protein (150 kDa) and GAPDH (38 kDa). (D) Western blot analysis indicates nearly absent PTPRF in the proband. Data are represented as mean ± SEM. * indicates P < 0.05 (independent 1-taliled t-test) using GAPDH as a control.