Baculoviral IAP Repeat-Containing Protein 1

Description

NAIP, HIAP1, HIAP2, XIAP, BIRC5, and BIRC6 are members of the mammalian inhibitors of apoptosis family and contain an N-terminal domain with 1 to 3 imperfect repeats of an approximately 65-amino acid domain named the baculovirus IAP repeat (BIR) motif. The expression of NAIP in mammalian cells inhibits apoptosis induced by a variety of signals.

Molecular Genetics

Linkage studies in families of spinal muscular atrophy patients found that 95% of all cases of spinal muscular atrophy were linked to the 5q13 region of chromosome 5. Two candidate genes within this region were first described: the survival motor neuron (SMN) gene and neuronal apoptosis inhibitory protein gene. Each of these genes was found to be present in at least two copies.

The frequency of homozygous deletion of the intact NAIP gene was found to be different in SMA type I and type II/III (45% versus 18%), thus leading to the suggestion that the severity of the disease may depend on the deletion of the NAIP gene.

Analysis of both the SMN and NAIP genes is significantly complicated by the existence of highly homologous genes that limit the ability of the currently used tests to detect only homozygous deletion of these genes.

Epidemiology in the Arab World

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Other Reports

Bahrain

A study conducted by Haider et al. (2001) on the pattern of exon deletion in the NAIP gene in Spinal Muscular Dystrophy included three Bahraini SMA patients [See Kuwait > Haider et al., 2001].

Kuwait

Samilchuk et al. (1996) carried out deletion analysis of the SMN and NAIP genes in 11 cases of type I SMA and in 4 type II SMA cases. The patients were of Kuwaiti origin. They also analyzed samples from 41 healthy relatives of these patients and 44 control individuals of Arabic origin. Exon 5 of the NAIP gene was homozygously absent in all type I SMA patients but was retained in the type II patients. They reported that among relatives one mother was homozygously deleted for NAIP. All of the control individuals had normal SMN and NAIP. Samilchuk et al. (1996) noted that there findings are consistent with the previously reported observations that the incidence of NAIP deletion is much higher in the clinically more severe cases (type I SMA) than in the milder forms, and all of the type II SMA patients in their study had at least one copy of the intact NAIP gene.

Haider and Moosa (1997) investigated the presence of survival motor neuron gene and neuronal apoptosis inhibitory protein gene deletions in 17 Arab and 1 Indian families with spinal muscular atrophy (15 type I and 3 type II). Homologous deletions were detected in exons 7 and 8 of the survival motor neuron gene and exon 5 of the neuronal apoptosis inhibitory protein gene in all patients with type I spinal muscular atrophy. Exon 13 of the neuronal apoptosis inhibitory protein gene was deleted in only one patient with type I spinal muscular atrophy. In two patients with type II spinal muscular atrophy, only exons 7 and 8 of the survival motor neuron gene were deleted whereas exons 5 and 13 of the neuronal apoptosis inhibitory protein gene were present. In another patient with spinal muscular atrophy type II, exons 7 and 8 of the survival motor neuron gene and exon 5 of the neuronal apoptosis inhibitory protein gene were deleted. This latter patient also had the Pierre Robin syndrome. No deletion was detected in healthy siblings or the parents.

Haider et al. (2001) investigated the pattern of exon deletion in survival motor neuron (SMN) genes in 46 patients with different phenotypes of spinal muscular atrophy from different ethnic backgrounds, which included 26 Kuwaiti patients. NAIP gene exons 5, 6, and 13 were intact in 20 out of the 21 Type II SMA patients, while one patient showed deletion of both exons 5 and 6. In patients with Type I SMA, 22 out of 23 patients had deletions of both exons 5 and 6 of NAIP gene, while only one patient had deletion of exon 13 of NAIP gene. The patient with intact exons 5 and 6 of NAIP gene had early onset of the disease with a severe course reflecting the absence of relationship between severity of the disease and NAIP gene deletions. None of the 62 controls had deletions of NAIP gene.

Oman

A study conducted by Haider et al. (2001) on the pattern of exon deletion in the NAIP gene in Spinal Muscular Dystrophy included five Omani SMA patients [See Kuwait > Haider et al., 2001].

Saudi Arabia

A study conducted by Haider et al. (2001) on the pattern of exon deletion in the NAIP gene in Spinal Muscular Dystrophy included one Saudi SMA patient [See Kuwait > Haider et al., 2001].

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