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Early onset or syndromic epilepsy v2.491 HERC2 Sarah Leigh Tag for-review was removed from gene: HERC2.
Early onset or syndromic epilepsy v2.491 HERC2 Sarah Leigh commented on gene: HERC2
Early onset or syndromic epilepsy v2.490 HERC2 Sarah Leigh Source Expert Review Green was added to HERC2.
Rating Changed from Amber List (moderate evidence) to Green List (high evidence)
Early onset or syndromic epilepsy v2.334 HERC2 Arina Puzriakova Phenotypes for gene: HERC2 were changed from Mental retardation, autosomal recessive 38 (MIM 615516) to Mental retardation, autosomal recessive 38, OMIM:615516
Early onset or syndromic epilepsy v2.129 HERC2 Arina Puzriakova Classified gene: HERC2 as Amber List (moderate evidence)
Early onset or syndromic epilepsy v2.129 HERC2 Arina Puzriakova Added comment: Comment on list classification: There is enough evidence for this gene to be rated GREEN at the next major review - more than 3 distinct variants in unrelated cases presenting the relevant phenotype.
Early onset or syndromic epilepsy v2.129 HERC2 Arina Puzriakova Gene: herc2 has been classified as Amber List (Moderate Evidence).
Early onset or syndromic epilepsy v2.128 HERC2 Arina Puzriakova Tag for-review tag was added to gene: HERC2.
Early onset or syndromic epilepsy v2.122 HERC2 Konstantinos Varvagiannis gene: HERC2 was added
gene: HERC2 was added to Genetic epilepsy syndromes. Sources: Literature
Mode of inheritance for gene: HERC2 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: HERC2 were set to 23065719; 23243086; 30902390; 32571899; 27848944; 26077850; 27759030
Phenotypes for gene: HERC2 were set to Mental retardation, autosomal recessive 38 (MIM 615516)
Penetrance for gene: HERC2 were set to Complete
Review for gene: HERC2 was set to GREEN
Added comment: Biallelic pathogenic HERC2 variants cause Mental retardation, autosomal recessive 38 (MIM 615516).

The current review is based mostly on the information provided by Elpidorou et al (2020 - PMID: 32571899) summarizing the findings in several affected individuals as published in the literature. ID was a universal feature among them (27/27) and seizures were reported in some (9/27):
- 22 subjects from Amish/Mennonite families were homozygous for p.Pro594Leu [NM_004667.5(HERC2):c.1781C>T] (Puffenberger et al 2012 - PMID: 23065719, Harlalka et al 2013 - PMID: 23243086, Abraham et al - PMID: 30902390)
- 2 additional patients were homozygous for another missense SNV [NM_004667.5(HERC2):c.4625G>A - p.Arg1542His] (Abraham et al 2019 - PMID: 30902390)
- 3 sibs born to consanguineous parents, homozygous for NM_004667.5:c.13767_13770delTGAA - p.(Asn4589LysTer4598)] as described by Elpidorou et al.
- 1 male homozygous 286 kb deletion spanning several 5' exons of HERC2 as well as the first exons of OCA2 was described by Morice-Picard et al (2016 - PMID: 27759030). Despite a neurological presentation (axial hypotonia, peripheral hypertonia, extrapyramidal symptoms and uncoordinated movements) further information was not available.

Apart from the cases summarized by Elpidorou et al, there have been few additional ones e.g. :
- Trujillano et al (2017 - PMID: 27848944) reported briefly on a patient, homozygous for NM_004667.5:c.4676-1G>A displaying seizures, hypotonia, global DD, "Encephalopathy" and abnormality of the liver.
- Yavarna et al (2015 - PMID: 26077850) provided few details with on an individual with primarily 'neurocognitive' phenotype but rather atypical presentation (MRI abnormalities, TGA, VSD, renal anomaly, growth retardation, hearing loss) due to p.Q3164X variant (recessive inheritance was specified).

Several lines of evidence support an important role for the protein encoded (an E3 ubiquitin protein ligase, interacting also with UBE3A, involved in several cellular processes incl. cell cycle regulation, spindle formation during mitosis, mitochondrial functions, DNA damage responses by targeting proteins such as XPA) as well as the effect of the reported variants (mRNA studies, Western blot, detection of a fusion transcript in the case of the deletion, etc).

Individuals from the Amish families displayed Angelman-like features (in line with HERC2-UBE3A interaction) with - among others - gait instability. Mouse models recapitulate some of these features (e.g. the movement disorder) as extensively discussed by Abraham et al.

Overall this gene can be included in the ID and epilepsy panels with green rating.
Sources: Literature