Generation of induced pluripotent stem cell lines from two unrelated patients affected by intellectual disability carrying homozygous variants in SGIP1.

Intellectual disability (ID) is a diverse neurodevelopmental condition and almost half of the cases have a genetic etiology. SGIP1 acts as an endocytic protein that influences the signaling of receptors in neuronal systems related to energy homeostasis through its interaction with endophilins. This study focuses on the generation and characterization of induced pluripotent stem cells (iPSC) from two unrelated patients due to a frameshift variant (c.764dupA, NM_032291.4) and a splice donor site variant (c.74 + 1G > A, NM_032291.4) in the SGIP1 gene.

Homozygous novel truncating variant of CLPP associated with severe Perrault syndrome.

A female proband and her affected niece are homozygous for a novel frameshift variant of CLPP. The proband was diagnosed with severe Perrault syndrome encompassing hearing loss, primary ovarian insufficiency, abnormal brain white matter and developmental delay.

New insights into Perrault syndrome, a clinically and genetically heterogeneous disorder.

Hearing loss and impaired fertility are common human disorders each with multiple genetic causes. Sometimes deafness and impaired fertility, which are the hallmarks of Perrault syndrome, co-occur in a person. Perrault syndrome is inherited as an autosomal recessive disorder characterized by bilateral mild to severe childhood sensorineural hearing loss with variable age of onset in both sexes and ovarian dysfunction in females who have a 46, XX karyotype. Since the initial clinical description of Perrault syndrome 70 years ago, the phenotype of some subjects may additionally involve developmental delay, intellectual deficit and other neurological disabilities, which can vary in severity in part dependent upon the genetic variants and the gene involved. Here, we review the molecular genetics and clinical phenotype of Perrault syndrome and focus on supporting evidence for the eight genes (CLPP, ERAL1, GGPS1, HARS2, HSD17B4, LARS2, RMND1, TWNK) associated with Perrault syndrome. Variants of these eight genes only account for approximately half of the individuals with clinical features of Perrault syndrome where the molecular genetic base remains under investigation. Additional environmental etiologies and novel Perrault disease-associated genes remain to be identified to account for unresolved cases. We also report a new genetic variant of CLPP, computational structural insight about CLPP and single cell RNAseq data for eight reported Perrault syndrome genes suggesting a common cellular pathophysiology for this disorder. Some unanswered questions are raised to kindle future research about Perrault syndrome.

Exploring the potential role of disease-causing mutation in a gene desert: duplication of noncoding elements 5' of GRIA3 is associated with GRIA3 silencing and X-linked intellectual disability.

GRIA3 encodes glutamate receptor ionotropic AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) subunit 3 and has been previously involved in X-linked intellectual disability (ID). We report on a male proband with ID and epilepsy associated with a duplication mapping within a gene desert, 874-kb upstream of the GRIA3 gene. This 970-kb duplication is maternally inherited. The proband's mother has a skewed X chromosome-inactivation pattern in agreement with her normal cognitive function. Quantitative polymerase chain reaction analysis indicates absence of GRIA3 mRNA in the proband lymphocytes relative to a wild-type control. Centromeric to the duplicated region, comparative genomic analysis showed a 2268-bp evolutionarily conserved region that could be a critical transcription factor binding-site for GRIA3 expression. The repositioning of distant-acting sequences, rather a missense/nonsense mutation, is considered to be causative for GRIA3-linked ID. This study illustrates the importance of high-resolution array-Comparative Genomic Hybridization analysis in exploring the potential role of disease-causing mutation in functional noncoding sequences.