PTCH1 duplication in a family with microcephaly and mild developmental delay

Area of Science:

• Genetics
• Genomic Medicine
• Developmental Biology

Background:

• Genomic deletions are more common than duplications, with submicroscopic duplications historically underdiagnosed due to limited detection methods.
• Advances in array comparative genomic hybridization (array CGH) now allow sensitive detection of chromosomal microduplications, revealing novel genetic syndromes.

Purpose of the Study:

• To identify the genetic cause of developmental delay, failure to thrive, and microcephaly in a young boy.
• To investigate the role of chromosomal microduplications, specifically involving the PTCH1 gene, in neurodevelopmental disorders.

Main Methods:

• Utilized a clinical targeted oligonucleotide array (CMA-V6.3 OLIGO) for high-resolution chromosomal analysis.
• Sequenced chromosomal breakpoints to precisely characterize the identified duplication, including its size, location, and orientation.

Main Results:

• Identified a ~360-kb tandem duplication in the 9q22.32 region in a 21-month-old boy exhibiting developmental delay, failure to thrive, and microcephaly.
• The same duplication was present in the patient's mother, who also presented with microcephaly and mild developmental delay.
• The duplicated segment encompasses the entire PTCH1 gene, a gene known to be involved in developmental pathways.

Conclusions:

• The identified PTCH1 gene duplication may contribute to phenotypes such as microcephaly and developmental delay, potentially through gain-of-function mechanisms.
• Suggests that PTCH1 duplication should be considered in the differential diagnosis for individuals with unexplained microcephaly or holoprosencephaly.
• Highlights the importance of advanced array-based technologies in uncovering previously unrecognized genetic causes of developmental disorders.