Table 1. Defects of mitochondrial transcription, pre-RNA, mRNA processing and stabilization.

Gene	Protein	Clinical presentation	Age of onset	Mode of inheritance	OMIM	References
TFAM	Transcription factor A	Mitochondrial DNA depletion syndrome 15	Infancy	AR	617156	Stiles et al. (2016) [12]
TRMT10C	tRNA methyltransferase 10	Combined OXPHOS deficiency 30	Infancy	AR	616974	Metodiev et al. (2016) [13]
HSD17B10 (MRPP2)	NAD(P)(H)-dependent short-chain dehydrogenase/reductases	Global developmental delay, epilepsy, and cardiac involvement	Early childhood	AR	300256	Oerum et al. (2017) [14], Falk et al. (2016) [15]
ELAC2	RNase Z	Hypertrophic cardiomyopathy, hypotonia, lactic acidosis, delayed psychomotor development	Early childhood	AR	605367	Haack et al. (2013) [16], Shinwari et al. (2017) [17], Akawi et al. (2016) [18]
FASTKD2	fas activated serine-threonine kinase domain 2 protein	Later onset, milder MELAS (mitochondrial encephalomyopathy, lactic acidosis and stroke-like episode)-like syndrome with seizures, stroke-like episodes and optic atrophy. Mitochondrial encephalomyopathy with developmental delay, hemiplegia, convulsions, asymmetrical brain atrophy	Childhood	AR	612322	Ghezzi et al. (2008) [19], Yoo et al. 2017 [20]
MTPAP	Mitochondrial poly-A polymerase	Progressive spastic ataxia with optic atrophy	Juvenile or early childhood	AR	613672	Crosby et al. (2010) [21]
LRPPRC	Leucine-rich PPR-motif containing protein	Leigh syndrome French–Canadian variant (LSFC)	Infantile	AR	220111	Mootha et al. (2003) [22], Olahova et al. (2015) [23], Han et al. (2017) [24]

OMIM, Online Mendelian Inheritance in Man; AR, autosomal recessive.